#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
const int MAX = 1e5 + 55;
const int INF = 1e9 + 77;
const long long INFINF = 1e18 + 1e17;
const double PI = acos(-1.0);
long long power(long long x, long long y) {
  if (y == 0) return 1;
  long long s = power(x, y / 2);
  s *= s;
  if (y & 1) s *= x;
  return s;
}
int n, m, t;
int x[100];
long long dp[100][100][100];
long long solve(int i, int howb, int howg) {
  if (i == n) {
    if (howb + howg == t) {
      if (howb >= 4 && howg >= 1) {
        return 1;
      }
    }
    return 0;
  }
  long long &res = dp[i][howb][howg];
  if (res != -1) {
    return res;
  }
  res = 0;
  if (x[i]) {
    res += solve(i + 1, howb + 1, howg);
    res += solve(i + 1, howb, howg);
  } else {
    res += solve(i + 1, howb, howg + 1);
    res += solve(i + 1, howb, howg);
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m >> t;
  for (int i = 0; i < n; i++) {
    x[i] = 1;
  }
  n += m;
  memset(dp, -1, sizeof(dp));
  cout << solve(0, 0, 0);
  return 0;
}
