#include <bits/stdc++.h>
using namespace std;
long long z, j, n, m, t, s = 0, i, a[30], b[30], x, y, k;
long long c(long long n, long long r) {
  z = 1;
  x = 0;
  y = 0;
  for (j = max(r, n - r) + 1; j <= n; j++) a[x++] = j;
  j = min(r, n - r);
  while (j) b[y++] = j--;
  for (k = 0; k < y; k++)
    for (j = x - 1; j >= 0; j--)
      if (a[j] % b[k] == 0) {
        a[j] /= b[k];
        b[k] = 1;
        break;
      }
  for (j = 0; j < x; j++) z *= a[j];
  for (j = 0; j < y; j++) z /= b[j];
  return z;
}
int main() {
  cin >> n >> m >> t;
  for (i = 4; i <= n; i++)
    if (t - i <= m && t - i > 0) s += c(n, i) * c(m, t - i);
  cout << s;
  return 0;
}
