#include <bits/stdc++.h>
using namespace std;
int n, m, k;
int main() {
  cin >> n >> m >> k;
  if (k >= m) {
    printf("1.00000\n");
    return 0;
  } else if (k + n < m) {
    printf("0\n");
    return 0;
  }
  double ans = 1.0;
  int i;
  for (i = 0; i <= k; i++) ans = ans * ((double)(m - i) / (n + 1 + i));
  ans = 1.0 - ans;
  printf("%.9lf\n", ans);
  return 0;
}
