#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=101;
int main()
{
int n,a[110],ans=0;
cin>>n;
a[0]=0;
for (int i=1;i<=n;i++)
{
scanf("%d",&a[i]);
if(a[i]>a[i-1])
ans+=(a[i]-a[i-1])*6+5;
else
ans+=(a[i-1]-a[i])*4+5;
}
printf("%d",ans);
}