#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

float dp[10001];

int main(){
    int H, A, D;
    cin >> H >> A >> D;
    rep(i, H)dp[i+1] = 1e5;
    rep(i, H){
        smin(dp[min(H, i + A)], dp[i] + 1);
        smin(dp[min(H, i + D)], dp[i] + 1.5f);
    }
    printf("%0.5f\n", dp[H]);
}