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C(N,M) = N!/(M!*(N-M)!)
#include<stdio.h>
int n ,m;
double fact(int n)
{
double ans = 1;
for (int i = 2; i <= n; ++i) ans *= i;
return ans;
}
int main()
{
scanf("%d%d", &n, &m);
printf("%.0lf\n", fact(n) / fact(m) / fact(n - m));
}