#include <bits/stdc++.h>
using namespace std;
const long long MAXN = 60;
long long comb[MAXN][MAXN];
long long komb(int a, int b) {
  if (b == 0 || b == a) return comb[a][b] = comb[a][a - b] = 1;
  if (comb[a][b]) return comb[a][b];
  comb[a][b] = comb[a][a - b] = (komb(a - 1, b) + komb(a - 1, b - 1));
  return comb[a][b];
}
int main() {
  long long n, m, t;
  cin >> n >> m >> t;
  for (int i = 1; i <= 31; i++)
    for (int j = 0; j <= i; j++) komb(i, j);
  long long res = 0;
  for (int i = 4, j; i <= n; i++) {
    j = t - i;
    if (j > m) continue;
    if (j < 1) continue;
    res += comb[n][i] * comb[m][j];
  }
  cout << res << endl;
}
