#include<iostream>
#include<iomanip>
#include<cmath>
#include <algorithm>
using namespace std;
void Ahmed_Negm(){
  #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
  #endif
}
int main()
{Ahmed_Negm();

double n, k, kiwi, blue, straw, res;
cin>>n>>k;
kiwi = (n*2)/k;
blue = (n*5)/k;
straw = (n*8)/k;
res = ceil(kiwi) + ceil(blue) + ceil(straw);
cout<<res;




    return 0;
}