#include <bits/stdc++.h>
using namespace std;
long double lg[100100];
int n, m, k;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n >> m >> k;
  if (m < k + 1) {
    cout << "1.000000000000" << endl;
    return 0;
  }
  for (int i = 1; i <= 100020; i++) {
    lg[i] = lg[i - 1] + logl(i);
  }
  long double tot = lg[n] + lg[m] - lg[n + k + 1] - lg[m - k - 1];
  cout << fixed << setprecision(20)
       << max(1.0000 - expl(tot), (long double)(0.00000)) << endl;
  return 0;
}
