#include <bits/stdc++.h>
using namespace std;
void __print(int32_t x) { cout << x; }
void __print(long long x) { cout << x; }
void __print(long double x) { cout << x; }
void __print(double x) { cout << x; }
void __print(float x) { cout << x; }
void __print(bool x) { cout << (x ? "true" : "false"); }
void __print(char x) { cout << '\'' << x << '\''; }
void __print(const char *x) { cout << '\"' << x << '\"'; }
void __print(const string &x) { cout << '\"' << x << '\"'; }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cout << '{';
  __print(x.first);
  cout << ',';
  __print(x.second);
  cout << '}';
}
template <typename T>
void __print(const T &x) {
  long long f = 0;
  cout << '{';
  for (auto &i : x) cout << (f++ ? "," : ""), __print(i);
  cout << "}";
}
void _print() { cout << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cout << ", ";
  _print(v...);
}
long long power(long long base, long long exp) {
  long long res = 1;
  base %= 1000000007;
  while (exp > 0) {
    if (exp & 1) res = (res * base) % 1000000007;
    base = (base * base) % 1000000007;
    exp = exp >> 1;
  }
  return res;
}
long long inv(long long x) { return power(x, 1000000007 - 2) % 1000000007; }
const long long N = 1e3 + 3, M = N;
long long i, j;
long long dp[N][M];
long long ncr(long long n, long long r) {
  if (r > n) return 0;
  if (n == r or r == 0) return 1;
  if (dp[n][r] != -1) return dp[n][r];
  return dp[n][r] = ncr(n - 1, r - 1) + ncr(n - 1, r);
}
void solve() {
  long long n, m, t;
  cin >> n >> m >> t;
  fill(&dp[0][0], &dp[0][0] + N * M, -1);
  long long sm = 0;
  for (i = 1; i <= m; i++) {
    long long g = i, b = t - g;
    if (b <= n and b >= 4) {
      sm += ncr(n, b) * ncr(m, g);
    }
  }
  cout << sm << '\n';
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) solve();
  return 0;
}
