#include <bits/stdc++.h>
using namespace std;
unsigned long long x1, out;
unsigned long long Fac(unsigned long long x1) {
  unsigned long long out = 1;
  for (int i = 1; i <= x1; i++) out = out * i;
  return out;
}
unsigned long long Cnk(unsigned long long a, unsigned long long b,
                       unsigned long long c) {
  unsigned long long outL = 1;
  vector<int> fac;
  if (b > c) {
    unsigned long long nCount = a - b;
    for (int i = 2; i <= c; i++) fac.push_back(i);
    while (nCount > 0) {
      outL = outL * a;
      a--;
      nCount--;
      for (int i = 0; i < fac.size(); i++) {
        if (fac[i] > -1 && outL % fac[i] == 0) {
          outL = outL / fac[i];
          fac[i] = -1;
        }
      }
    }
  } else {
    unsigned long long nCount = a - c;
    for (int i = 2; i <= b; i++) fac.push_back(i);
    while (nCount > 0) {
      outL = outL * a;
      a--;
      nCount--;
      for (int i = 0; i < fac.size(); i++) {
        if (fac[i] > -1 && outL % fac[i] == 0) {
          outL = outL / fac[i];
          fac[i] = -1;
        }
      }
    }
  }
  for (int i = 0; i < fac.size(); i++) {
    if (fac[i] > -1) outL = outL / fac[i];
  }
  return outL;
}
int main() {
  int n, m, t;
  cin >> n >> m >> t;
  for (int i = 4; i <= n; i++) {
    for (int y = 1; y <= m; y++) {
      if (i + y != t) continue;
      out += (Cnk(n, i, n - i) * Cnk(m, y, m - y));
    }
  }
  cout << out;
  cin >> x1;
}
