#include <bits/stdc++.h>
using namespace std;
const int M = 1000000007;
int n, m, t;
long long dp[61][31][31];
int arr[61];
long long solve(int ind, int x, int y) {
  if (x > 3 && y > 0 && x + y == t) return 1;
  if (ind == n + m + 1) return 0;
  long long &ret = dp[ind][x][y];
  if (ret != -1) return ret;
  ret = solve(ind + 1, x, y);
  if (x < n && arr[ind] == 1) ret += solve(ind + 1, x + 1, y);
  if (y < m && arr[ind] == 2) ret += solve(ind + 1, x, y + 1);
  return ret;
}
int main() {
  scanf("%d%d%d", &n, &m, &t);
  int i = 0;
  for (; i < n; i++) arr[i] = 1;
  for (; i < n + m; i++) arr[i] = 2;
  memset(dp, -1, sizeof dp);
  printf("%lld\n", solve(0, 0, 0));
  return 0;
}
