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>
int main()
{
    int a[1000],temp,i,j,k=0,m,n,b;
    scanf("%d",&n);
    for(i=0;i<n-1;i++)
    {
        scanf("%d",&a[i]);
    }
    m=a[n-2];
    int l=n-1;
    for(i=0;i<l;i++)
    {
        if(a[i]==0)
        {
            i++;
            //continue;
        }
        else if(a[i]>=a[i+1])
        {
           a[i]=a[i+1];
           k=k+a[i];
        }
        else if(a[i+1]>a[i])
        {
            a[i+1]=a[i];
            k=k+a[i];
        }
    }
    k=k+m;
    printf("%d\n",k);
    return 0;
}