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>

#define N 10000000

int main() {
	int i, n, b[N], ans = 0;

	scanf("%d", &n);

	for (i = 0; i < n- 1; i++) {
		scanf("%d", &b[i]);
	}

	for (i = n-2; i >=0; i--) {
      if(n != 2){
		if (b[i] > b[i + 1]) {
			ans += b[i + 1];
		}
		else {
			ans += b[i];
		}
      }
      else{
      	ans += b[0];
        break;
      }
	}
  
	ans += b[n - 2];

	printf("%d\n", ans);
	
	return 0;
}