#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, k;
  cin >> n >> m >> k;
  double res = 1;
  if (k >= m)
    cout << 1 << endl;
  else if (k + n < m)
    cout << 0 << endl;
  else {
    for (int i = 0; i < k + 1; i++) res = res * (m - i) / (n + i + 1);
    cout << fixed << setprecision(8) << 1 - res << endl;
  }
}
