#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n, m, k;
  scanf("%d%d%d", &n, &m, &k);
  double res = 1;
  int st = m - k;
  int fi = n + 1;
  if (m <= k) {
    printf("1\n");
    return 0;
  }
  while ((st <= m) && (fi <= (n + k + 1))) {
    res *= st;
    res /= fi;
    st++;
    fi++;
  }
  while (st <= m) {
    res *= st;
    st++;
  }
  while (fi <= (n + k + 1)) {
    res /= fi;
    fi++;
  }
  if (res > 1) res = 1;
  printf("%.4lf\n", 1 - res);
  return 0;
}
