#include <bits/stdc++.h>
using namespace std;
int n, m, k;
double qwq = 1;
int main() {
  cin >> n >> m >> k;
  if (m <= k) return printf("1"), 0;
  for (int i = 0; i <= k; i++) qwq *= (m - k + i) * 1.0 / (n + 1 + i);
  cout << max(1 - qwq, 0.0);
  return 0;
}
