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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)


import javax.swing.text.StringContent;
import java.util.*;

public class Main {

    /* チェックリスト
     * 結果はintの範囲を超えていませんか？(必要な時以外はlongを使いましょう)
     * TLEしそうな処理はありませんか？
     */
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        long n = Integer.parseInt(sc.nextLine());
        List<Integer> input = new ArrayList<Integer>();
        for(long i = 0; i < n - 1;i++){
            input.add(Integer.parseInt(sc.next()));
        }
        long max = 0;
        //nが3
        //3回試行して 2 2 5
        int cur = 0;
        long prev = Integer.MAX_VALUE;
        long r = 0;
        for(int i : input){
            if(i > prev){
                r += prev;
            }else{
                r += i;
            }
            prev = i;
            cur++;
        }
        System.out.println(r + input.get(input.size() - 1));
    }
}