#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    int H,A,D;
    cin >> H >> A >> D;
    double ans = INF;
    int N = (H + A + 1) / A;
    for(int i = 0;i <= N;i++){
        if(H < 0)H = 0;
        ans = min(ans, i + ( (H + D - 1) / D * (3. / 2)) );
        H -= A;
    }
    /*
    ans = min(ans , (H + D - 1) / D * (3. / 2) );
    ans = min(ans , (H + A - 1) / A * 1.);
    */
    cout << ans << endl;
}