#include <bits/stdc++.h>
using namespace std;
long double l[200006];
int main() {
  l[1] = 0;
  l[0] = 0;
  for (int i = 2; i < 200005; i++) {
    l[i] = log(i) + l[i - 1];
  }
  int n, m, k;
  scanf("%d%d%d", &n, &m, &k);
  if (k >= m) {
    printf("1.00000\n");
  } else if (k + n < m) {
    printf("0.00000\n");
  } else {
    long double ans = l[n] + l[m] - l[n + k + 1] - l[m - k - 1];
    ans = exp(ans);
    double tmp = 1.0 - ans;
    printf("%.10f\n", tmp);
  }
  return 0;
}
