#include <bits/stdc++.h>
int main() {
  int n, m, k;
  scanf("%d%d%d", &n, &m, &k);
  if (k >= m)
    printf("%.6lf\n", 1.0);
  else if (n + k < m)
    printf("%.6lf\n", 0.0);
  else {
    double r = 1.0;
    for (int i = 0; i <= k; ++i) r *= (double)(m - i) / (n + i + 1);
    printf("%.6lf\n", 1 - r);
  }
  return 0;
}
