#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

int n,arr[1000000],arr2[1000000];

int main(){
	scanf("%d",&n);
	for(int i=0;i<n-1;i++){
		scanf("%d",&arr[i]);
	}
	arr2[0]=arr[0];
	for(int i=0;i<n;i++){
		if(i==n-1){
			arr2[i+1]=arr[i];
		}else{
			if(arr[i]<arr2[i]){
				arr2[i]=arr[i];
			}
			arr2[i+1]=arr[i];
		}
	}
	long sum;
	for(int i=0;i<n;i++){
//		printf("%d",arr2[i]);
		sum+=arr2[i];
	}
	printf("%ld",sum);
	
	return 0;
} 