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: Accepted)

package main

import (
	"fmt"
)

func main() {

	var N int

	fmt.Scan(&N)

	B := SliceInt(N - 1)

	for i := 0; i < N-1; i++ {

		fmt.Scan(&B[i])

	}

	result :=0

	result += B[0]+B[N-2]

	for i:=1;i<=N-2;i++{

		result += min(B[i-1],B[i])
	}

	fmt.Println(result)

}

// return min
func min(a,b int) int{

	if a>b{

		return b
	}

		return a	
 
}

//SliceInt 引数サイズのSliceを返す
func SliceInt(a int) []int {

	IntSample := make([]int, a)

	return IntSample

}