using System;

class CalculateNKNK
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        int k = int.Parse(Console.ReadLine());
        int nSubK = n - k;

        ulong factN = GetFactorialN(n);
        ulong factK = GetFactorialK(k);
        ulong factNSubK = GetFactorialNSubK(nSubK);

        if (1 < k && k < n && n < 100)
        {
            ulong result = 1;
            result = factN / (factK * factNSubK);
            Console.WriteLine(result);
        }
    }

    private static ulong GetFactorialN(int n)
    {
        if (n == 0)
        {
            return 1;
        }
        return (ulong)n * GetFactorialN(n - 1);
    }

    private static ulong GetFactorialK(int k)
    {
        if (k == 0)
        {
            return 1;
        }
        return (ulong)k * GetFactorialK(k - 1);
    }

    private static ulong GetFactorialNSubK(int nSubK)
    {
        if (nSubK == 0)
        {
            return 1;
        }
        return (ulong)nSubK * GetFactorialNSubK(nSubK - 1);
    }
}