#include <bits/stdc++.h>
using namespace std;
double n, m, k;
int main() {
  while (scanf("%lf %lf %lf", &n, &m, &k) != EOF) {
    if (m > n + k) {
      printf("%.6lf\n", 0.0);
      continue;
    }
    double resp = 1.0;
    for (int i = 0; i <= k; i++) {
      resp *= ((m - i) / (n + k + 1 - i));
    }
    printf("%.6lf\n", 1.0 - resp);
  }
  return 0;
}
