#include <bits/stdc++.h>
using namespace std;
double a[100 * 2 + 10];
int n, m, k;
double f(int x) {
  if (x <= 200) return a[x];
  return x * log(x) - x + 0.5 * log(2 * x * 3.141592653589);
}
int main() {
  a[0] = 0;
  for (int i = 1; i <= 2 * 100; i++) a[i] = a[i - 1] + log(i);
  while (scanf("%d%d%d", &n, &m, &k) != EOF) {
    if (n + k < m) {
      printf("0\n");
      continue;
    }
    if (k - m >= 0) {
      printf("1\n");
      continue;
    } else {
      double t = exp(f(m) + f(n) - f(m - k - 1) - f(n + k + 1));
      printf("%.6lf\n", 1.0 - t);
    }
  }
}
