static public void Problem24()
        {
            //A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of the digits 1, 2, 3 and 4.If all of the permutations are listed numerically or alphabetically, we call it lexicographic order.The lexicographic permutations of 0, 1 and 2 are:
            //012   021   102   120   201   210
            //What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 ?

            bool[] isUsed = new bool[10];
            int[] permutation = new int[10];

            StringBuilder sb = new StringBuilder();

            //(╥_╥)
            int count = 0;
            for (int a = 0; a < 10; a++)
            {
                isUsed[a] = true;

                for (int b = 0; b < 10; b++)
                {
                    if (isUsed[b])
                    {
                        continue;
                    }
                    else
                    {
                        isUsed[b] = true;
                        for (int c = 0; c < 10; c++)
                        {
                            if (isUsed[c])
                            {
                                continue;
                            }
                            else
                            {
                                isUsed[c] = true;
                                for (int d = 0; d < 10; d++)
                                {
                                    if (isUsed[d])
                                    {
                                        continue;
                                    }
                                    else
                                    {
                                        isUsed[d] = true;
                                        for (int e = 0; e < 10; e++)
                                        {
                                            if (isUsed[e])
                                            {
                                                continue;
                                            }
                                            else
                                            {
                                                isUsed[e] = true;
                                                for (int f = 0; f < 10; f++)
                                                {
                                                    if (isUsed[f])
                                                    {
                                                        continue;
                                                    }
                                                    else
                                                    {
                                                        isUsed[f] = true;
                                                        for (int g = 0; g < 10; g++)
                                                        {
                                                            if (isUsed[g])
                                                            {
                                                                continue;
                                                            }
                                                            else
                                                            {
                                                                isUsed[g] = true;
                                                                for (int h = 0; h < 10; h++)
                                                                {
                                                                    if (isUsed[h])
                                                                    {
                                                                        continue;
                                                                    }
                                                                    else
                                                                    {
                                                                        isUsed[h] = true;
                                                                        for (int i = 0; i < 10; i++)
                                                                        {
                                                                            if (isUsed[i])
                                                                            {
                                                                                continue;
                                                                            }
                                                                            else
                                                                            {
                                                                                isUsed[i] = true;
                                                                                for (int j = 0; j < 10; j++)
                                                                                {
                                                                                    if (isUsed[j])
                                                                                    {
                                                                                        continue;
                                                                                    }
                                                                                    else
                                                                                    {
                                                                                        count++;
                                                                                        isUsed[j] = true;

                                                                                        sb.Clear();
                                                                                        if (count == 1000000)
                                                                                        {
                                                                                            permutation[0] = a;
                                                                                            permutation[1] = b;
                                                                                            permutation[2] = c;
                                                                                            permutation[3] = d;
                                                                                            permutation[4] = e;
                                                                                            permutation[5] = f;
                                                                                            permutation[6] = g;
                                                                                            permutation[7] = h;
                                                                                            permutation[8] = i;
                                                                                            permutation[9] = j;

                                                                                            for (int r = 0; r < 10; r++)
                                                                                            {
                                                                                                sb.Append(permutation[r]);
                                                                                            }
                                                                                            Console.Write(sb + "");
                                                                                            goto end;
                                                                                        }
                                                                                    }
                                                                                    isUsed[j] = false;
                                                                                }
                                                                            }
                                                                            isUsed[i] = false;
                                                                        }
                                                                    }
                                                                    isUsed[h] = false;
                                                                }
                                                            }
                                                            isUsed[g] = false;
                                                        }
                                                    }
                                                    isUsed[f] = false;
                                                }
                                            }
                                            isUsed[e] = false;
                                        }
                                    }
                                    isUsed[d] = false;
                                }
                            }
                            isUsed[c] = false;
                        }
                    }
                    isUsed[b] = false;
                }
                isUsed[a] = false;
            }
            end:;
        }