#include <bits/stdc++.h>
using namespace std;
int main() {
  int p, q, k, i;
  double res = 1;
  cin >> p >> q >> k;
  if (q <= k)
    res = 0;
  else if (p + k < q)
    res = 1;
  else {
    for (i = q - k; i <= q; ++i) res *= i;
    for (i = p + 1; i <= p + k + 1; ++i) res /= i;
  }
  res = 1 - res;
  cout << res << '\n';
  return 0;
}
