#include <iostream>
#include <iomanip>
using namespace std;
int main(){
  int h,a,d;cin>>h>>a>>d;
  int nw = 0;
  double ret = (h+a-1)/a;
  while(h >= 0){
    int count = (h+d-1)/d;
    double expect = (double)count*3/2;
    ret = min(ret,expect+nw);
    h -= a;
    nw++;
  }
  cout << fixed << setprecision(10) <<  ret << endl;
}