Problem:
Score : 300 points

Problem Statement

You've come to your favorite store Infinitesco to buy some ice tea.

The store sells ice tea in bottles of different volumes at different costs.
Specifically, a 0.25-liter bottle costs Q yen, a 0.5-liter bottle costs H yen, a 1-liter bottle costs S yen, and a 2-liter bottle costs D yen.
The store has an infinite supply of bottles of each type.

You want to buy exactly N liters of ice tea. How many yen do you have to spend?

Constraints

1 \leq Q, H, S, D \leq 10^8

1 \leq N \leq 10^9

All input values are integers.

Input

Input is given from Standard Input in the following format:

Q H S D
N

Output

Print the smallest number of yen you have to spend to buy exactly N liters of ice tea.

Sample Input 1

20 30 70 90
3

Sample Output 1

150

Buy one 2-liter bottle and two 0.5-liter bottles. You'll get 3 liters for 90 + 30 + 30 = 150 yen.

Sample Input 2

10000 1000 100 10
1

Sample Output 2

100

Even though a 2-liter bottle costs just 10 yen, you need only 1 liter.
Thus, you have to buy a 1-liter bottle for 100 yen.

Sample Input 3

10 100 1000 10000
1

Sample Output 3

40

Now it's better to buy four 0.25-liter bottles for 10 + 10 + 10 + 10 = 40 yen.

Sample Input 4

12345678 87654321 12345678 87654321
123456789

Sample Output 4

1524157763907942

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <algorithm>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define FOR(i,k,n) for (int (i)=(k); (i)<(n); ++(i))
#define RFOR(i,k,n) for (int (i)=(n)-1; (i)>=(k); --(i))
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define pb push_back
#define mp make_pair
#define fst first
#define snd second
#define all(v) v.begin(), v.end()
#define debug(x) cerr<< #x <<": "<<x<<endl
#define debug2(x,y) cerr<< #x <<": "<< x <<", "<< #y <<": "<< y <<endl
using namespace std;
typedef long long int LL;

int main() {
  LL q,h,s,d,n,ans = 0;
  cin >> q >> h >> s >> d >> n;
  vector<pair<LL, LL> > tea;
  tea.pb(mp(4 * q, q));
  tea.pb(mp(2 * h, h));
  tea.pb(mp(s, s));
  tea.pb(mp(d / 2, d));
  sort(all(tea));
  REP(i, 4) {
    float quantity = (float)tea[i].snd / tea[i].fst;
    LL num = (quantity >= 1) ? floor(n / (int)quantity) : floor(n * (int)(1 / quantity));
    n -= num * quantity;
    ans += num * tea[i].snd;
    if(n == 0) break;
  }
  cout << ans << endl;

  return 0;
}