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