#include <fstream>
using namespace std;
ifstream fin ("date.in");
ofstream fout ("date.out");

int main()
{
    unsigned long int a[500][500]={0};
    int i,j,k,n;
    fin>>n>>k;
    a[0][0]=1;
    for(i=1;i<=n;i++)
        for(j=0;j<=i;j++)
            if(j==0 || j==i) a[i][j]=1;
            else a[i][j]=a[i-1][j]+a[i-1][j-1];

    fout<<a[n][k]<<endl;
    fin.close();
    fout.close();
    return 0;
}