#include <bits/stdc++.h>
using namespace std;
const double eps = 0.000000000000001;
int main() {
  int n, m, k;
  scanf("%d%d%d", &n, &m, &k);
  long double ans = 1;
  if (n - m + k < 0) {
    printf("0\n");
    return 0;
  }
  if (m == 0) {
    printf("1\n");
    return 0;
  }
  int i;
  for (i = 0; i <= k; i++) {
    ans = (ans * (m - i) / (n + 1 + i));
  }
  ans = 1 - ans;
  printf("%.6lf\n", (double)ans);
  return 0;
}
