#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
string toBin(long long a) {
  string res = "";
  while (a) {
    res += char((a & 1) + '0');
    a >>= 1;
  }
  reverse(res.begin(), res.end());
  return res;
}
const int mod = 1e9 + 7;
long long expo(long long base, long long pow) {
  long long ans = 1;
  while (pow != 0) {
    if (pow & 1 == 1) {
      ans = ans * base;
      ans = ans % mod;
    }
    base *= base;
    base %= mod;
    pow /= 2;
  }
  return ans;
}
double pi = 3.141592653589793238462643;
double error = 0.0000001;
const int M = 100001;
const int MOD = 1e9 + 7;
long long fac[100], ifac[100];
long long PowerMod(long long a, long long n) {
  long long ret = 1;
  while (n) {
    if (n & 1) {
      ret *= a;
      ret %= MOD;
    }
    a *= a;
    a %= MOD;
    n /= 2;
  }
  return ret;
}
inline void precompute() {
  int i;
  fac[0] = 1;
  for (i = 1; i < 100; i++) {
    fac[i] = (i * fac[i - 1]) % MOD;
  }
  ifac[100 - 1] = PowerMod(fac[100 - 1], MOD - 2);
  for (i = 100 - 2; i >= 0; i--) {
    ifac[i] = ((i + 1) * ifac[i + 1]) % MOD;
  }
}
long long com(int n, int r) {
  long long ret = fac[n];
  ret *= ifac[r];
  ret %= MOD;
  ret *= ifac[n - r];
  ret %= MOD;
  return ret;
}
int main() {
  precompute();
  int n, m, t;
  cin >> n >> m >> t;
  long long ans = 0;
  for (int b = 4; b <= n; b++) {
    for (int g = 1; g <= m; g++) {
      if ((b + g) != t) continue;
      long long temp = com(n, b) * com(m, g);
      ans += temp;
    }
  }
  cout << ans;
}
