import java.io.*;
import java.util.*;

class Main {

    public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        long N;
        N = sc.nextLong();
        long[] B = new long[(int)(N-1)];
        for(int i = 0 ; i < N-1 ; i++){
                B[i] = sc.nextLong();
        }
        solve(N, B);
    }

    static void solve(long N, long[] B){
        long ans = 0;
        ans += B[0];
        for (int i = 1; i < B.length; i++) {
            ans += Math.min(B[i], B[i-1]);
        }
        ans += B[B.length - 1];
        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