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 Go (1.6) (judge verdict: Wrong Answer)

package main

import "fmt"
func minInt(a, b int) int{
	if a < b{return a}
	return b
}

func main(){
	var N , max int
	var B[100000] int
	var A[100000] int

	fmt.Scan(&N)

	for i := 0 ; i < N - 1 ; i++ {
		fmt.Scan(&B[i])
	}
	A[0] = B[0]
	for i := 1 ; i < N-1 ; i++ {
		A[i] = minInt(B[i-1], B[i])
	}
	A[N-1] = B[N-2]
	for i := 0 ; i < N ; i++ {
		max += A[i]
		fmt.Printf("%d ", A[i])
	}
	fmt.Println()
	fmt.Println(max)
	
}