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 Java7 (OpenJDK 1.7.0) (judge verdict: Wrong Answer)

 
import java.util.Scanner;

 class Main{
	public static void main(String[]args) {
		Scanner scan = new Scanner(System.in) ;
		int n = scan.nextInt();
		long arr2[] = new long[n] ;
		long arr1[] = new long[n-1] ; 
		for(int i = 0 ; i < n-1 ; i++) {
			arr1[i] = scan.nextInt();
		}
		arr2[arr2.length-1] = arr1[arr1.length -1] ;
		for(int i = arr2.length-2 ; i>0 ; i--) {
			if(arr1[i-1] <=arr2[i+1]) {
				arr2[i] = arr1[i-1];
			}else {
				arr2[i] = arr2[i+1];
			}
			//System.out.println(i) ;
		}
		arr2[0] = arr2[1] ;
		long sum = 0 ;
		for(int i = 0 ; i <arr2.length ; i++) {
			sum+=arr2[i] ;
		}
		System.out.println(sum) ;
	}
}