#include <bits/stdc++.h>
using namespace std;
inline long long rd() {
  long long x = 0, w = 1;
  char ch = 0;
  while (ch < '0' || ch > '9') {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = (x << 3) + (x << 1) + (ch ^ 48);
    ch = getchar();
  }
  return x * w;
}
long long n, k;
int main() {
  n = rd(), k = rd();
  cout << (n * 2 + k - 1) / k + (n * 5 + k - 1) / k + (n * 8 + k - 1) / k
       << endl;
  return 0;
}
