#include <bits/stdc++.h>
using namespace std;
long long pd[100][100][100];
int t, B, G;
int v[100];
long long solve(int pos, int b, int g) {
  if (pd[pos][b][g] != -1) return pd[pos][b][g];
  if (b + g == t) {
    if (g >= 1 && b >= 4) return 1;
    return 0;
  }
  if (pos == G + B) return 0;
  long long ans = 0;
  if (v[pos] == 1)
    ans += solve(pos + 1, b, g + 1);
  else
    ans += solve(pos + 1, b + 1, g);
  ans += solve(pos + 1, b, g);
  return pd[pos][b][g] = ans;
}
int main() {
  memset(v, 0, sizeof(v));
  memset(pd, -1, sizeof(pd));
  scanf("%d %d %d", &B, &G, &t);
  for (int i = 0; i < G; i++) v[i] = 1;
  cout << solve(0, 0, 0) << endl;
  return 0;
}
