Codeforces Beta Round #95 (Div. 2)C. The World is a Theatre

#include 
#include 
#include 
#include 
using namespace std;
long long n, m, t;

long long C(long long x, long long y)
{
    long long q = 1, sum = 1;
    for(int i = x+1; i <= y; i++)
    {
        sum = sum*i/q;
        q++;
    }
    return sum;
}

int main()
{
    cin >> n >> m >> t;
    long long s = 0;
    for(int i = 4; i <= n; i++)
    {
        if(i <= n && t-i<=m && t-i>0)
        {
            s = s + C(i, n)*C(t-i, m);
        }
    }
    cout << s << endl;
}