#include <bits/stdc++.h>                                                                        
                                                                                                
using namespace std;                                                                            
                                                                                                
#define all(x) x.begin(), x.end()                                                               
#define rep(i, n) for (int i = 0; i < n; ++i)                                                   
#define reps(i, m, n) for (int i = m; i <= n; ++i)                                              
                                                                                                
using i64 = long long;                                                                          
using pii = pair<i64, i64>;                                                                     
                                                                                                
template<class A, class B>inline bool chmax(A &a, const B &b){return b > a ? a = b,1 : 0;}      
template<class A, class B>inline bool chmin(A &a, const B &b){return b < a ? a = b,1 : 0;}      
                                                                                                
constexpr int INF = 0x3f3f3f3f;                                                                 
constexpr i64 LINF = 0x3f3f3f3f3f3f3f3fLL;                                                      
constexpr int MOD = int(1e9) + 7;                                                               
                                                                                                
using P = pair<double, pair<int, double>>;                                                      
                                                                                                
signed main()                                                                                   
{                                                                                               
  ios::sync_with_stdio(false);                                                                  
  cin.tie(nullptr);                                                                             
                                                                                                
  i64 q, h, s, d;                                                                               
  cin >> q >> h >> s >> d;                                                                      
                                                                                                
  chmin(h, 2 * q);                                                                              
  chmin(s, 2 * h);                                                                              
                                                                                                
  i64 N;                                                                                        
  cin >> N;                                                                                     
  i64 case1 = s * N;                                                                            
  i64 case2 = d * (N / 2) + s * (N % 2);                                                        
                                                                                                
  cout << min(case1, case2) << "\n";                                                            
                                                                                                
  return 0;                                                                                     
}                                                                                               

Measured memory_bytes: 256