#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;
    ans = min(ans , (H + D - 1) / D * (3. / 2) );
    ans = min(ans , (H + A - 1) / A * 1.);

    cout << ans << endl;
}