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