#include <bits/stdc++.h>
using namespace std;
int n, m, k;
double ans = 1;
int main() {
  cin >> n >> m >> k;
  if (m > n + k)
    ans = 1;
  else if (m <= k)
    ans = 0;
  else {
    for (int i = 0; i < k + 1; i++) ans *= (double)(m - i) / (n + k + 1 - i);
  }
  cout << fixed << setprecision(6) << 1 - ans << endl;
  return 0;
}
