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 PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
$n = trim(fgets(STDIN));
$b = explode(" ", trim(fgets(STDIN)));

$count = 0;
if($n == 2){
    $count += $b[0] *2;
}elseif($n == 3){
    $count += $b[0] *2;
    $count += $b[count($b)-1];
}else{
    $count += $b[0] *2;
    for($i=0; $i<count($b)-1; $i++){
        $count += min($b[$i],$b[$i+1]);
    }
    $count += $b[count($b)-1];
}


echo $count;

?>