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 java.util.Scanner;
//import java.util.Arrays;
public class Main{
  public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int[] b = new int[a-1];
    int[] c = new int[a];
    int ans = 0;
    for(int i = 0;i < b.length;i++){
      b[i] = sc.nextInt();
    }
    c[0] = b[0];
    c[a-1] = c[a-2];
    for(int j = 1;j<b.length;j++){
      if(b[j-1] <= b[j]){
        c[j] = b[j-1];
      }else{
        c[j] = b[j];
      }
      c[a-1] = b[a-2];
    }
    //System.out.println(Arrays.toString(c));
    for(int x = 0;x < c.length;x++){
      ans +=c[x];
    }
    System.out.println(ans);
  }
}