import java.util.*;

class Main{
	public static void main(String[] $){
		Scanner s=new Scanner(System.in);
		int n=s.nextInt();
		long r=0;
		int[] b=new int[n];
		Arrays.fill(b,100000);
		for(int i=1;i<n;++i){
			int a=s.nextInt();
			b[i-1]=Math.min(b[i-1],a);
			b[i]=Math.min(b[i],a);
		}
		System.out.println(Arrays.stream(b).sum());
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz