#include <bits/stdc++.h>
using namespace std;
long long n, m, K;
int main() {
  cin >> n >> m >> K;
  long double ans = 1.0;
  if (n - m + K < 0) return puts("0");
  for (int k = 0; k <= K; ++k) {
    ans *= 1.0 * (m - k);
    ans /= 1.0 * (n + k + 1);
  }
  ans = 1. - ans;
  cout << setprecision(16);
  cout << fixed;
  cout << ans << "\n";
}
