#include <bits/stdc++.h>
using namespace std;
int n, m, k;
double ans = 1;
int main() {
  scanf("%d%d%d", &n, &m, &k);
  if (k >= m) return printf("1\n") & 0;
  if (n + k < m) return printf("0\n") & 0;
  for (int i = 1; i <= k + 1; i++) ans = ans * (m - i + 1) / (n + i);
  ans = 1.0 - ans;
  printf("%.4f\n", ans);
  return 0;
}
