//denote表示 specified明确规定  requests要求 single line单线,单行

//The numbers denote at which floors the elevator will stop, 
//in specified order.
//数字表示电梯将按指定顺序停靠在哪些楼层。

//For a given request list对于给定的请求列表
#include<iostream>

using namespace std;

int main()
{
    int n;
    cin>>n;
    int ans = 0;
    int former = 0;
    for(int i = 0; i<n; i++)
    {
        int x;
        cin>>x;
        if(x-former>0) ans+=(x-former)*6;
        else ans+=(x-former)*(-4);
        former = x;
    }
    ans+=n*5;
    cout<<ans;
    return 0;
}