#include <bits/stdc++.h>
using namespace std;
const int D = 507;
const int Inf = 1000000007;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, m, k;
  cin >> n >> m >> k;
  long double res1 = 1, res2 = 1;
  for (int i = m; i >= m - k; i--) res1 *= (long double)i;
  for (int i = n + 1; i <= n + k + 1; i++) res2 *= (long double)i;
  cout << fixed << setprecision(6)
       << max((long double)0, ((long double)1 - (res1 / res2))) << "\n";
}
