#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9;
const long long MOD = 1e9 + 7;
long long n, m, k;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> m >> k;
  if (m <= k) {
    cout << "1.00000000\n";
    return 0;
  } else {
    if (n + k < m) {
      cout << "0.000000000\n";
      return 0;
    }
    long double res = 1.0;
    long double atas = 1;
    int sek = n + 1;
    for (int i = m - k; i <= m; i++) {
      atas *= i;
      if (sek <= (n + k + 1)) {
        atas /= (sek++);
      }
    }
    cout << setiosflags(ios::fixed) << setprecision(10) << res - atas << '\n';
  }
}
