#include <bits/stdc++.h>
using namespace std;
long long n, m, k;
long double t = 1;
int main() {
  cin >> n >> m >> k;
  if (n + k + 1 > n + m) {
    cout << "1";
    return 0;
  }
  if (n - m + k < 0) {
    cout << "0";
    return 0;
  }
  for (long long i = n + 1; i <= n + k + 1; i++) {
    t = t * (n + m - i + 1) / i;
  }
  setprecision(10);
  cout << 1 - t;
  return 0;
}
