#include <bits/stdc++.h>
using namespace std;
int k,a[105],b[105],s=0,j;
int main(){
	cin>>k;
	for(j=1;j<k;j++){cin>>a[j+1];}
	a[1]=a[2];
	for(j=1;j<k;j++)
	{
		b[j]=min(a[j+1],a[j]);
		s+=b[j];
	}
	cout<<s+a[k]<<endl;
	return 0;
}