#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <string.h>
#include <fstream>
#include <assert.h>

using namespace std;


#define LL long long
#define N 1001000
#define M 2000100
#define MP make_pair
#define Pi acos(-1.0)
//#pragma comment(linker,"/S    TACK:1024000000,1024000000")
#define ls (rt << 1)
#define rs (ls | 1)
#define md ((ll+rr)/2)
#define lson ls,ll,md
#define rson rs,md+1,rr
#define mod 1000000007
#define inf 0x3f3f3f3f
#define sqr(x) ((x)*(x))
#define eps 1e-6
#define ULL unsigned long long
LL powmod(LL a,LL b) {LL res=1;a%=mod;for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
#define F(x) ((x)/3+((x)%3 == 1 ? 0 : tb))
#define G(x) ((x)<tb ? (x)*3+1 : ((x) - tb)*3+2)
#define lowbit(x) ((x)&(-x))
#define fi first
#define se second
#define pii pair<int,int>
#define pil pair<int,LL>
#define pli pair<LL,int>
#define pb push_back
#define sf(n) scanf("%d", &n)
//#define ss set<int>::iterator

int gcd(int x,int y){
    while(y){
        int t = x % y;
        x = y;
        y = t;
    }
    return x;
}

template<typename T> inline bool chkmin(T &a, const T &b) { return a > b ? a = b, 1 : 0; }
template<typename T> inline bool chkmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }

namespace FastIO {
#define BUF_SIZE 200010 //缓冲区大小可修改
    bool IOError = 0; //IOError == false 时表示处理到文件结尾
    inline char NextChar() {
        static char buf[BUF_SIZE], *p1 = buf + BUF_SIZE, *pend = buf + BUF_SIZE;
        if(p1 == pend) {
            p1 = buf;
            pend = buf + fread(buf, 1, BUF_SIZE, stdin);
            if(pend == p1) {
                IOError = 1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool Blank(char c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t';
    }
    
    inline void read(int &x){
        bool sign=0; char ch=NextChar(); x=0;
        for (;Blank(ch);ch=NextChar());
        if (IOError)return;
        if (ch=='-')sign=1,ch=NextChar();
        for (;ch>='0'&&ch<='9';ch=NextChar())x=x*10+ch-'0';
        if (sign)x=-x;
    }
    inline void read(long long &x){
        bool sign=0; char ch=NextChar(); x=0;
        for (;Blank(ch);ch=NextChar());
        if (IOError)return;
        if (ch=='-')sign=1,ch=NextChar();
        for (;ch>='0'&&ch<='9';ch=NextChar())x=x*10+ch-'0';
        if (sign)x=-x;
    }
    inline void read(double &x){
        bool sign=0; char ch = NextChar(); x=0;
        for (;Blank(ch);ch = NextChar());
        if (IOError)return;
        if (ch=='-')sign=1,ch=NextChar();
        for (;ch>='0'&&ch<='9';ch=NextChar())x=x*10+ch-'0';
        if (ch=='.'){
            double tmp=1; ch=NextChar();
            for (;ch>='0'&&ch<='9';ch=NextChar())tmp/=10.0,x+=tmp*(ch-'0');
        }
        if (sign)x=-x;
    }
    inline void read(char *s){
        char ch=NextChar();
        for (;Blank(ch);ch=NextChar());
        if (IOError)return;
        for (;!Blank(ch)&&!IOError;ch=NextChar())*s++=ch;
        *s=0;
    }
    inline void read(char &c){
        for (c=NextChar();Blank(c);c=NextChar());
        if (IOError){c=-1;return;}
    }
}
using namespace FastIO;

int main()
{
    int q, h, s, d, n;
    read(q), read(h), read(s), read(d), read(n);
    
    q *= 4, h *= 2;
    chkmin(q, h);
    chkmin(q, s);
    if(q * 2 < d)
    {
        printf("%lld\n",1LL * n * q);
    }
    else
    {
        printf("%lld\n",1LL * d * (n / 2) + q * (n % 2));
    }
    
    return 0;
}

Measured memory_bytes: 256