#include <bits/stdc++.h>
template <typename T, typename U>
inline void swap(T &a, U &b) {
  a = a ^ b;
  b = a ^ b;
  a = a ^ b;
}
inline void swap(int &a, int &b) {
  a = a ^ b;
  b = a ^ b;
  a = a ^ b;
}
inline void smax(int &a, int b) {
  if (b > a) a = b;
}
inline void smin(int &a, int b) {
  if (b < a) a = b;
}
inline int gcd(int a, int b) {
  if (a < b) swap(a, b);
  while (b > 0) {
    a -= a / b * b;
    swap(a, b);
  }
  return a;
}
long long nchose(int a, int b) {
  long long ans = 1;
  smax(a, b - a);
  int p = 2;
  for (int i = (b - a + 1); i <= (b); i++) {
    ans *= (long long)i;
    while (p <= a && ans % p == 0) ans /= p++;
  }
  return ans;
}
using namespace std;
long long n, m, t;
int main() {
  cin >> n >> m >> t;
  long long ans = 0;
  for (int i = (4); i <= (n); i++) {
    int j = t - i;
    if (j < 1 || j > m) continue;
    ans += nchose(i, n) * nchose(j, m);
  }
  cout << ans;
}
