#include <bits/stdc++.h>
typedef long long ll;
int main() {
    ll n, k;
    scanf("%lld%lld\n", &n, &k);
    printf("%lld\n", (n * 2 + k - 1) / k + (n * 5 + k - 1) / k + (n * 8 + k - 1) / k);
    return 0;
}