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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val n = sc.nextInt()
    val b = (0 until n - 1).map { sc.next().toInt() }
    println(problem140c(n, b))
}

fun problem140c(n: Int, b: List<Int>): Long {
    val dp = (0 until n).map { 0L }.toMutableList()
    dp[0] = b[0].toLong()
    for (i in 1 until n) {
        if (i >= n - 2) {
            dp[i] += b[i - 1].toLong()
        } else {
            dp[i] = Math.min(b[i], b[i - 1]).toLong()
        }
    }
    return dp.sum()
}