#include <bits/stdc++.h>
using namespace std;
int n, m, k;
int main() {
  scanf("%d%d%d", &n, &m, &k);
  long double ans1 = 1, ans2 = 1;
  for (int i = m - k; i <= m; i++) ans1 *= i;
  for (int i = n + 1; i <= n + k + 1; i++) ans2 *= i;
  if (ans1 > ans2)
    puts("0.00000000");
  else {
    double ans = (ans2 - ans1) / ans2;
    printf("%.8lf\n", ans);
  }
  return 0;
}
