#include<bits/stdc++.h>
#define rep(i,a,n) for (int i = a; i < n; i++)
#define per(i,n,a) for (int i = n - 1; i >= a; i--)
using namespace std;

double dp[20000];
int main() {
    int h, a, d;
    cin >> h >> a >> d;
    rep(i, 1, h + 1) {
        dp[i] = min(dp[max(0, i - a)] + 1, dp[max(0, i - d)] + 1.5);
    }
    printf("%.1f\n", dp[h]);
}