#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
using namespace std;
long long exp(long long x, long long y, long long p) {
  x %= p;
  long long res = 1;
  while (y) {
    if (y % 2) res = (res * x % p) % p;
    x = (x * x) % p;
    y /= 2;
  }
  return res;
}
long long expo(long long x, long long y) {
  long long res = 1;
  while (y) {
    if (y % 2) res = (res * x % 1000000007) % 1000000007;
    x = (x * x) % 1000000007;
    y /= 2;
  }
  return res;
}
long long add(long long a, long long b) {
  return (a % 1000000007 + b % 1000000007 + 1000000007) % 1000000007;
}
long long sub(long long a, long long b) {
  return (a % 1000000007 - b % 1000000007 + 1000000007) % 1000000007;
}
long long mul(long long a, long long b) {
  return ((a % 1000000007) * (b % 1000000007) + 1000000007) % 1000000007;
}
long long inv(long long x) { return expo(x, 1000000007 - 2); }
void timelap();
vector<long long> pascal[31];
void buildpascal() {
  pascal[1].push_back(1);
  pascal[1].push_back(1);
  for (long long i = 2; i <= 30; i++) {
    pascal[i].push_back(1);
    for (long long j = 1; j < i; j++)
      pascal[i].push_back(pascal[i - 1][j] + pascal[i - 1][j - 1]);
    pascal[i].push_back(1);
  }
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(0);
  long long n, m, t;
  cin >> n >> m >> t;
  buildpascal();
  long long res = 0;
  for (long long i = 4; i <= n; i++) {
    long long temp = t - i;
    if (temp < 1) break;
    if (temp > m) continue;
    res += (pascal[n][i] * pascal[m][temp]);
  }
  cout << res << '\n';
  timelap();
  return 0;
}
void timelap() {}
