#include <bits/stdc++.h>
using namespace std;
long long fact(long long n);
long long modularexponentiation(long long a, long long b, long long m) {
  long long result = 1;
  while (b > 0) {
    if (b % 2 == 1) result = (result * a) % m;
    a = (a * a) % m;
    b = b / 2;
  }
  return result;
}
long long binaryexponentiation(long long a, long long b) {
  long long result = 1;
  while (b > 0) {
    if (b % 2 == 1) result = (result * a);
    a = (a * a);
    b = b / 2;
  }
  return result;
}
long long nCr(long long n, long long r) {
  return fact(n) / (fact(r) * fact(n - r));
}
long long binomialCoeff(long long n, long long k) {
  long long C[n + 1][k + 1];
  long long i, j;
  for (i = 0; i <= n; i++) {
    for (j = 0; j <= min(i, k); j++) {
      if (j == 0 || j == i)
        C[i][j] = 1;
      else
        C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
    }
  }
  return C[n][k];
}
long long fact(long long n) {
  long long res = 1;
  for (long long i = 2; i <= n; i++) res = res * i;
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  while (t--) {
    long long n, m, t, ans = 0;
    cin >> n >> m >> t;
    long long i;
    for (i = 4; i <= n && i <= t; i++) {
      long long boys = i, girls = t - i;
      if (girls <= m && girls >= 1 && girls <= t)
        ans += binomialCoeff(n, boys) * binomialCoeff(m, girls);
    }
    cout << ans;
  }
}
