#include <bits/stdc++.h>
using namespace std;
inline long long read() {
  char c = getchar();
  long long x = 0;
  bool f = 0;
  for (; !isdigit(c); c = getchar()) f ^= !(c ^ 45);
  for (; isdigit(c); c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
  if (f) x = -x;
  return x;
}
long long n, m, k;
signed main() {
  n = read(), m = read(), k = read();
  if (n - m + k < 0) return puts("0"), 0;
  if (k >= m) return puts("1"), 0;
  double ans = 1;
  k++;
  for (long long i = 1; i <= k; i++) ans = ans * (m - i + 1) / (n + i);
  ans = 1 - ans;
  printf("%.8lf", ans);
  return 0;
}
