import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int N = stdIn.nextInt();
		int[] B = new int[N-1];
		long sum = 0;
		B[0] = stdIn.nextInt();
		sum += B[0];
		
		for(int i = 1; i < N-1; i++) {
			B[i] = stdIn.nextInt();
			if(B[i-1] >= B[i]) sum += B[i];
			else sum += B[i-1];
		}
		sum += B[N-2];
		
		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