#include<stdio.h>

int main()
{
	long m, n, i, k = 1, sum = 1, count = 0;
	int ques;

	while (scanf("%ld %ld", &n, &m) != EOF)
	{
		k = 1;
		sum = 1;
		for (i=m+1; i<=n; i++)
			k *= i;

		for (i=n-m; i>=2; i--)
			sum *= i;
	
		ques = k /sum;
		printf("%d\n", ques);
	}

	return 0;
}