#include <bits/stdc++.h>   using namespace std;   unsigned long long B[31][31], res = 0;   int main(void) {     for (int i = 0; i <= 30; i++) {       B[i][0] = B[i][i] = 1;       for (int j = 1; j < i; j++) B[i][j] = B[i - 1][j - 1] + B[i - 1][j];     }     int n, m, k;     cin >> n >> m >> k;     for (int b = 4; b < k; b++) {       res += (b <= n && k - b <= m) ? B[n][b] * B[m][k - b] : 0;     }     cout << res;     return 0;   }   