string[,] mas0 = new string[100, 4];
        string[] mas1 = new string[100];
        int[] mas2 = new int[100];
private void FindBiggestSumm()
        {
            int maxCredit = mas2[0];
            int indexOfMC = 0;

            for (int i = 0; i < personList.Count; i++)
            {
                mas2[i] = int.Parse(mas1[i]);
            }

            if (personList.Count > 1)
            {
                for (int i = 0; i < personList.Count; i++)
                {
                    for (int j = personList.Count; j > i + 1; j--)
                    {
                        if (String.Compare(mas[i, 0], mas[j - 1, 0]) == 0)
                        {
                            int here = j - 1;
                            mas2[i] += mas2[j-1];

                            DeleteStringMas(ref here);
                        }
                    }
                }

                for (int i = 0; i < personList.Count; i++)
                {
                    if (mas2[i] > maxCredit)
                    {
                        maxCredit = mas2[i];
                        indexOfMC = i;
                    }
                }
            }

            MessageBox.Show("Максимальный кредит взят клиентом " + mas0[indexOfMC, 0] + " и составляет " + maxCredit + " рублей.");
            maxCredit = 0;
            indexOfMC = 0;
        }

        private void DeleteStringMas(ref int here)
        {
            int t;
            string[,] vs1 = new string[personList.Count, 4];

            for (int m = 0; m < personList.Count; m++)
            {
                for (int j = t = 0; j < 4; j++, t++)
                {
                    if (m != here)
                    {
                        vs1[m, t] = mas0[m, j];
                    }
                    else
                    {
                        j++;
                    }
                    vs1[m, t] = mas0[m, j];
                }
            }
            mas0 = new string[100, 4];
            mas0 = vs1;
        }