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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function myout(text){console.log(text);}//standard output
function Main(input) {
	input = input.trim();
	//input = input.trim().split(" ");
	input = input.trim().split("\n");
	//input = input.trim().split(" ").map((a)=>Number(a));
	//input = input.trim().split("\n").map((a)=>Number(a));
  var len = parseInt(input[0]) - 1;
  var b = input[1].split(" ").map((a)=>Number(a));
  var output = b[0] + b[len - 1];
  for(var i = 0; i < len - 1; i++){
    output += Math.min(b[i], b[i + 1]);
  }
  myout(output);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));