#include <iostream>
using namespace std;
typedef long long ll;

int H, A, D;

bool done[10010];
double dp[10010];

double solve(int h){
    if(h <= 0)return 0;
    if(done[h])return dp[h];
    
    double res = min(solve(h - A) + 1, solve(h - D) + 1.5);
    
    done[h] = true;
    return dp[h] = res;
}

int main(){
    cin >> H >> A >> D;
    
    printf("%.10f\n", solve(H));
    return 0;
}