import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int b[] = new int[n - 1];
		for ( int i = 0; i < n - 1; i++ ) {
			b[i] = in.nextInt();
		}

		int sum = 0;
		sum += b[0];
		sum += b[n - 2];
		
		for(int i = 1; i <= n-2; i++) {
			sum += Math.min(b[i], b[i-1]);
		}
		
		System.out.println(sum);

		in.close();

	}
}
/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