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: Runtime Error)

import java.util.*;
public class Main {
	public static void main(String[] args){
       Scanner sc = new Scanner(System.in);   
      //取得
	  int N = sc.nextInt();
      int[] B = new int[N-1];
      for(int i=0;i<N-1;i++){
        B[i] = sc.nextInt();
      }
      //Bの中身を変える
      for(int i=0;i<N-1;i++){
        if(B[i]>B[i+1]){
        B[i] = B[i+1];
        }
      }
      //Bの値をAに移す
      int[] A = new int[N];
      int sum = B[0];
      for(int i=1;i<N;i++){
          A[i]=B[i-1];
          sum+=A[i];
      }
      System.out.println(sum);
    }
}