#include <iostream>

using namespace std;

int main()

{

int n;

while(cin>>n)

{

int f[5001]={1};

for(int i=1; i<=n; i++) cin>>f[i];

int pc=0;

for(int i=1; i<=n; i++)

{

if(f[i]>f[i-1]) pc+=(f[i]-f[i-1])*3;

else pc+=(f[i-1]-f[i])*2;

}

cout<<pc<<endl;

}

}