/* -*- coding: utf-8 -*-
 *
 * 23.cc: No.23 技の選択 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_H = 10000;

/* typedef */

/* global variables */

double dp[MAX_H + 1];

/* subroutines */

/* main */

int main() {
  int h, a, d;
  cin >> h >> a >> d;

  // e[x] = 1 + e[x + a]
  // e[x] = 1 + e[x]/3 + 2*e[x + d]*2/3
  // -> 3*e[x] = 3 + e[x] + 2*e[x + d]
  // -> 2*e[x] = 3 + 2*e[x + d]
  // -> e[x] = 1.5 + e[x + d]

  dp[h] = 0.0;
  for (int i = h - 2; i >= 0; i--) {
    double d0 = 1 + dp[min(i + a, h)];
    double d1 = 1.5 + dp[min(i + d, h)];
    dp[i] = min(d0, d1);
  }

  printf("%.1lf\n", dp[0]);
  return 0;
}