#include <bits/stdc++.h>
using namespace std;
string t;
int ct, z;
vector<int> vi;
int gcd(int a, int b) {
  if (!b) return a;
  if (a % b == 0) return b;
  return gcd(b, a % b);
}
int main() {
  int a, b, k;
  cin >> a >> b >> k;
  if (a + k < b) {
    printf("0.0000000\n");
    exit(0);
  }
  if (!b) {
    printf("1.000000\n");
    exit(0);
  }
  double p = 1;
  for (int i = 0; i <= k; ++i) {
    p *= (1.0 * (b - i)) / (a + i + 1);
  }
  printf("%.6lf\n", 1 - p);
  return 0;
}
