#include <bits/stdc++.h>
using namespace std;
bool isPrime(long long int n) {
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0)
    return false;
  else {
    for (long long int i = 5; i * i <= n; i += 6) {
      if (n % i == 0 || n % (i + 2) == 0) return false;
    }
    return true;
  }
}
long long int sum(long long int n) {
  long long int i = 0, j = 0;
  while (n != 0) {
    j = n % 10;
    i += j;
    n = n / 10;
  }
  return i;
}
long long int count(long long int n) {
  long long int i = 0;
  while (n != 0) {
    n = n / 10;
    i++;
  }
  return i;
}
long long int maxsum(long long int n) {
  long long int i = 0, j, k;
  j = count(n) - 1;
  while (j != 0) {
    i = i * 10 + 9;
    j--;
  }
  return (sum(n - i) + sum(i));
}
int ones(int n) {
  int i = 0, j;
  while (n != 0) {
    j = n % 2;
    if (j == 1) i++;
    n = n / 2;
  }
  return i;
}
long long int d, x, y;
void extendedEuclid(long long int A, long long int B) {
  if (B == 0) {
    d = A;
    x = 1;
    y = 0;
  } else {
    extendedEuclid(B, A % B);
    long long int temp = x;
    x = y;
    y = temp - (A / B) * y;
  }
}
long long int modInverse(long long int A, long long int M) {
  extendedEuclid(A, M);
  return (x % M + M) % M;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  srand(time(NULL));
  long long int n, i, j, k;
  cin >> n >> k;
  cout << (long long int)(ceil((2 * n) / (long double)k) +
                          ceil((5 * n) / (long double)k) +
                          ceil((8 * n) / (long double)k));
}
