Problem:
Score : 300 points

Problem Statement

There is an integer sequence A of length N whose values are unknown.

Given is an integer sequence B of length N-1 which is known to satisfy the following:

B_i \geq \max(A_i, A_{i+1})

Find the maximum possible sum of the elements of A.

Constraints

All values in input are integers.

2 \leq N \leq 100

0 \leq B_i \leq 10^5

Input

Input is given from Standard Input in the following format:

N
B_1 B_2 ... B_{N-1}

Output

Print the maximum possible sum of the elements of A.

Sample Input 1

3
2 5

Sample Output 1

9

A can be, for example, ( 2 , 1 , 5 ), ( -1 , -2 , -3 ), or ( 2 , 2 , 5 ). Among those candidates, A = ( 2 , 2 , 5 ) has the maximum possible sum.

Sample Input 2

2
3

Sample Output 2

6

Sample Input 3

6
0 153 10 10 23

Sample Output 3

53

Solution in Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
 
public class Main{
	public static void main(String[] args){
	    Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
        //Bの値取得
        int b[] =new int[n -1];
		for(int i = 0; i < n - 1; i++){
			b[i] = sc.nextInt();
        }
        //Aの値取得
        int a[] =new int[n - 2];
        int total = b[0] + b[n - 2];
		for(int i = 0; i < (n - 2); i++){
			if(b[i] < b[i + 1]){
            	a[i] = b[i];
            }else if(b[i] > b[i + 1]){
            	a[i] = b[i + 1];
            }
        }
        //合計を求める
        for(int i = 0; i < n - 2; i++){
        	total += a[i];
        }
        System.out.println(total);
	}
}