#include <bits/stdc++.h>
using namespace std;
int N, M, K;
long double a = 1, b = 1;
int main() {
  cin >> N >> M >> K;
  if (N + K < M) {
    cout << 0 << endl;
    return 0;
  }
  for (int i = 1; i <= K + 1; i++) {
    a = a * (M - i + 1) / (N + i);
  }
  cout << fixed << setprecision(20) << 1 - a << endl;
  return 0;
}
