#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
using namespace std;
long long mod_exp(long long x, long long y, long long mm) {
  if (y == 0)
    return (1);
  else if (y % 2 == 0)
    return (mod_exp((x * x) % mm, y / 2, mm));
  else
    return ((x * mod_exp((x * x) % mm, (y - 1) / 2, mm)) % mm);
}
bool isPowerOfTwo(long long n) {
  if (n == 0) return false;
  return (ceil(log2(n)) == floor(log2(n)));
}
long long nCrModpDP(long long n, long long r, long long p) {
  long long C[r + 1];
  memset(C, 0, sizeof(C));
  C[0] = 1;
  for (long long i = 1; i <= n; i++) {
    for (long long j = min(i, r); j > 0; j--) C[j] = (C[j] + C[j - 1]) % p;
  }
  return C[r];
}
long long nCrModpLucas(long long n, long long r, long long p) {
  if (r == 0) return 1;
  long long ni = n % p, ri = r % p;
  return (nCrModpLucas(n / p, r / p, p) * nCrModpDP(ni, ri, p)) % p;
}
long long solve() {
  long long n, m, t;
  cin >> n >> m >> t;
  long long ans = 0;
  for (long long i = 4; i <= n; i++) {
    for (long long j = 1; j <= m; j++) {
      if (i + j == t) {
        ans += nCrModpLucas(n, i, 1000000007) * nCrModpLucas(m, j, 1000000007);
      }
    }
  }
  return ans;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << solve();
  return 0;
}
