import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int[] buff=new int[n];
		int sum=0;

		for(int i=0;i<n-1;i++) {
			buff[i]=sc.nextInt();
		}
		buff[n-1]=Integer.MAX_VALUE;
		for(int i=1;i<n;i++) {
			sum+=Math.min(buff[i-1],buff[i]);
			//System.out.println(sum);
		}
		System.out.println(sum+buff[0]);
	}
}


/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