#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import array


def solve(h, a, d):
    dp = array.array("d")
    dp.append(0.0)
    for i in range(1, h + 1):
        dp.append(min(1.0 + (dp[i - a] if i >= a else 0),
                      1.5 + (dp[i - d] if i >= d else 0)))
    return dp[h]


def main():
    h, a, d = map(int, input().split())
    print("{:.2f}".format(solve(h, a, d)))


if __name__ == '__main__':
    main()