#include <iostream>

using namespace std;

long long calComb(int k, int n){

long long result = 1;

for (int i=n-k+1; i<=n; i++){

result *= i;

}

for (int i=2; i<=k; i++){

result /= i;

}

return result;

}

int main(){

int k, n;

while (1){

cin>> k>> n;

if (k==-1 && n == -1)

break;

cout<<"To hop chap "<<k<<" cua "<<n<<" la:"<<endl;

cout<<calComb(k, n)<<endl;

}

return 0;

}