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: Wrong Answer)

function Main(input) {
  input = input.split("\n");
  n = input[0].split("");
  b = input[1].split(" ");
  a=0;
  var ans=0;
  for(var i=0; i<n; i++){
    if(i==0){
      a=Number(b[0]);
    }else if(i==n-1){
      a=Number(b[i-1]);
    }else if(Number(b[i])>Number(b[i-1])){
      a=Number(b[i-1]);
    }else{
      a=Number(b[i]);
    }
    ans=ans+a;
  }
  console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));