#include <bits/stdc++.h>
using namespace std;
template <typename T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
template <typename T>
T lcm(T a, T b) {
  return a * b / gcd(a, b);
}
void printDouble(double x, int n) {
  cout << fixed << setprecision(n);
  cout << x << endl;
}
const int MAXN = 5e6 + 5;
const int mod = 1e9 + 7;
long long product() { return 1; }
long long sum() { return 0; }
template <typename T, typename... Args>
T product(T a, Args... args) {
  return (a * product(args...)) % mod;
}
template <typename T, typename... Args>
T sum(T a, Args... args) {
  return (a + sum(args...)) % mod;
}
vector<vector<long long> > f(61, vector<long long>(61, -1));
long long C(int n, int k) {
  if (n < k) return 0;
  if (f[n][k] != -1) return f[n][k];
  if (k == 0) return 1;
  if (k == 1) return n;
  if (k > n / 2) return C(n, n - k);
  return f[n][k] = C(n - 1, k) + C(n - 1, k - 1);
}
int main() {
  std::ios::sync_with_stdio(false);
  int n, m, t;
  cin >> n >> m >> t;
  long long res(0);
  for (int i = 4; i <= t - 1; i++) res += C(n, i) * C(m, t - i);
  cout << res;
}
