import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner s = new Scanner(System.in);
        int n = s.nextInt();
        
        int[] bs = new int[n - 1];
        bs[0] = s.nextInt();
        
        int sum = bs[0];
        
        for (int i = 1; i < n - 1; i ++) {
            bs[i] = s.nextInt();
            if (bs[i] > bs[i - 1])
                sum += bs[i - 1];
            else
                sum += bs[i];
        }
        
        sum += bs[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