#include <bits/stdc++.h>
using namespace std;
long long sq(long long x) {
  long long k = sqrt(x);
  while (k * k < x) {
    k++;
  };
  while (k * k > x) {
    k--;
  }
  return k;
};
long long cb(long long x) {
  long long k = cbrt(x);
  while (k * k * k < x) {
    k++;
  };
  while (k * k * k > x) {
    k--;
  }
  return k;
};
const long long INF = (long long)(1e17);
const double PI = 3.141592653589793;
long long dx[4] = {-1, 0, 1, 0};
long long dy[4] = {0, 1, 0, -1};
string path = "URDL";
long long binomialCoeff(long long n, long long k) {
  long long C[k + 1];
  memset(C, 0, sizeof(C));
  C[0] = 1;
  for (long long i = 1; i <= n; i++) {
    for (long long j = min(i, k); j > 0; j--) C[j] = C[j] + C[j - 1];
  }
  return C[k];
}
void solve() {
  long long n, m, t;
  cin >> n >> m >> t;
  long long ans = 0;
  for (long long b = 4; b <= n; b++) {
    long long g = t - b;
    if (g < 1) continue;
    ans += binomialCoeff(n, b) * binomialCoeff(m, g);
  }
  cout << ans << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL);
  solve();
  return 0;
}
