#include <bits/stdc++.h>
using namespace std;
int sti(const string &s) {
  int x;
  stringstream ss(s);
  ss >> x;
  return x;
}
string its(const int &x) {
  string s;
  stringstream ss(s);
  ss << x;
  s = ss.str();
}
void sscan(string &str) {
  str = "";
  char str_c;
  scanf("%c", &str_c);
  while (!(str_c == '\n' || str_c == ' ')) {
    str += str_c;
    scanf("%c", &str_c);
  }
}
void sprint(const string &str) {
  int length = str.length();
  for (int i = 0; i < length; ++i) printf("%c", str[i]);
}
uint64_t fact(int x) {
  if (x < 2) return 1;
  return fact(x - 1) * x;
}
uint64_t C(int x, int y) {
  uint64_t c = 1;
  for (int i = 0; i < y; ++i) {
    c *= x - i;
    c /= i + 1;
  }
  return c;
}
int main() {
  int n, m, t;
  scanf("%d %d %d", &n, &m, &t);
  uint64_t res = 0;
  for (int i = 4; i <= n && i < t; ++i) {
    if (t - i > m) continue;
    res += C(n, i) * C(m, t - i);
  }
  printf("%I64u", res);
  return 0;
}
