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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>

#define NEW(p,n){p=malloc((n)*sizeof(p[0]));if(p==NULL){printf("not enough memory\n");exit(1);};}
//pの型の変数n個の要素分のメモリを確保し、そのアドレスをpに代入するマクロ

#define MIN(a,b) ((a) < (b) ? (a) : (b))

int main(void){
    int N;
    scanf("%d",&N);

    int* B;
    NEW(B,N);
    for(int i=0;i<N;i++){
        scanf("%d\n", &B[i]);
    }

    int ans;
    ans=B[0]; //A[0]=B[0]
    for(int i=1;i<N;i++){
        ans+=MIN(B[i-1],B[i]); //A[i]=min(B[i-1],B[i])
    }
    ans+=B[N-1]; //A[N]=B[N-1];
    
    printf("%d",ans);

    return 0;
}