import java.util.Scanner;

public class Main {
	public static void main(String args[]){

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();

		int a[] = new int[n];
		a[0] = sc.nextInt();

		int curentInt = a[0];
		int beforeCur = curentInt;
		for(int i = 1;i < (n - 1);i++) {
			curentInt = sc.nextInt();
			a[i] = (beforeCur > curentInt) ? curentInt :beforeCur;
			beforeCur = curentInt;
		}

		a[n - 1] = curentInt;

		long sum = java.util.Arrays.stream(a).sum();
		System.out.println(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