解題思路：
設置一個當前層、一個目標層，每次到達目標層後更新當前層和目標層。累加所需時間即可。
代碼：
#include <iostream>
using namespace std;
int main(){
int cur = 0, next, up = 6, down = 4, stay = 5, n, sum = 0;
cin>>n;
sum += stay*n;
for(int i = 0; i < n; i++){
cin>>next;
if(next > cur)
sum += up*(next-cur);
else
sum += down*(cur-next);
cur = next;
}
cout<<sum;
return 0;
}