import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        int[] B = new int[N-1];
        int[] A = new int[N];
        int ans = 0;

        for(int i=0; i<N-1; i++){
            B[i] = sc.nextInt();
        }
        A[0] = B[0];
        for(int i=1; i<N-1; i++){
            if(B[i]<=B[i-1]){
                A[i] = B[i];
            }
            else if(B[i]>B[i-1]){
                A[i] = B[i-1];
            }
        }
        A[N-1] = B[N-2];
        for(int i=0; i<N; i++){
            ans += A[i];
        }
        System.out.println(ans);
    }
}
/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