#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) {
  while (a && b) a > b ? a %= b : b %= a;
  return a + b;
}
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
long long fast_exp(long long base, long long exp) {
  long long res = 1;
  while (exp > 0) {
    if (exp % 2 == 1)
      res = ((res % 1000000007) * (base % 1000000007)) % 1000000007;
    base = ((base % 1000000007) * (base % 1000000007)) % 1000000007;
    exp /= 2;
  }
  return res % 1000000007;
}
long long A[100][100];
void compute() {
  int i = 0, j = 0;
  for (i = 0; i < 100; i++) {
    A[i][0] = 1;
    A[i][i] = 1;
  }
  for (i = 1; i < 100; i++) {
    for (j = 1; j < 100; j++) {
      A[i][j] = A[i - 1][j - 1] + A[i - 1][j];
    }
  }
}
const int INF = INT_MAX;
const long long INFL = LLONG_MAX;
int main() {
  std::ios::sync_with_stdio(0);
  cin.tie(0);
  compute();
  long long n, m, t, ans = 0;
  cin >> n >> m >> t;
  if (t < 5 || n < 4 || m < 1) {
    cout << "0" << '\n';
    return 0;
  }
  long long b, g;
  t -= 5;
  for (int i = 0; i <= t; i++) {
    b = 4 + i;
    g = 1 + t - i;
    ans += A[n][b] * A[m][g];
  }
  cout << ans << '\n';
  return 0;
}
