#include <bits/stdc++.h>   using namespace std;   map<pair<long long int, long long int>, int> m;   long long int comb(long long int n, long long int r) {     int k1, k2;     if (m[make_pair(n, r)] != 0) return m[make_pair(n, r)];     if (r > n) return 0;     if (n == r) return 1;     if (r == 0) return 1;     if (r == 1) return n;     k1 = comb(n - 1, r - 1);     k2 = comb(n - 1, r);     m[make_pair(n - 1, r - 1)] = k1;     m[make_pair(n - 1, r)] = k2;     return k1 + k2;   }   int main() {     long long int n, m, t, k1 = 0, k2 = 0, k3 = 0, sum = 0, i = 0, x, y;     cin >> n >> m >> t;     if ((n + m) < t) cout << 0;     if (n < 4 || m < 1) cout << 0;     for (x = 4; x <= t - 1; x++) {       if (m >= (t - x)) sum += (comb(n, x) * comb(m, t - x));     }     cout << sum;   }   