#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.setf(ios::fixed);
  cout.precision(8);
  int n, m, k;
  cin >> n >> m >> k;
  double p = 1.0;
  for (int i = 0; i <= k; ++i) p *= double(m - i) / double(n + 1 + i);
  cout << 1.0 - min(1.0, p) << endl;
}
