#include <bits/stdc++.h>
int n, m, k;
int main() {
  scanf("%d%d%d", &n, &m, &k);
  if (n + k < m)
    printf("0\n");
  else {
    double ans = 1;
    for (int i = 1; i <= k + 1; ++i) {
      ans *= ((double)(m - i + 1) / (n + i));
    }
    ans = 1.0 - ans;
    printf("%.4f\n", ans);
  }
}
