~cpp
#include <iostream>
using namespace std;
int f(int, int);
int main()
{
int r, c;
cout << " , ? : ";
cin >> r >> c;
cout << f(c, r) << endl;
return 0;
}
int f(int a, int b) //a b
{
if (a > b)
return 0;
else if (a == 1 || a == b + 1)
return 1;
else
return f(a, b - 1) + f(a - 1, b - 1);
}










