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: Accepted)


#include <stdio.h>;
//#include "Main.h"
int main(void)
{
	// Your code here!
	int n;
	long int a[101];
	long int b[101];
	long long int ans=0;
	long int min_num = 100001;
	int index;
	scanf("%d", &n);

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

	}
	for (int i = 0; i<n; i++)
	{
		a[i]=-1;
	}
	for (int i = 0; i<n-1; i++)
	{
		min_num = 100001;
		for (int j = 0; j < n-1; j++)
		{
			if (b[j]<=min_num)
			{
				index = j;
				min_num = b[j];
			}
		}
		
		if (a[index] == -1)
		{
			a[index] = b[index];
		}

		if (a[index+1] == -1)
		{
			a[index+1] = b[index];
		}
		b[index] = 100001;
	}
	for (int i = 0; i<n; i++)
	{
		//printf("%d", a[i]);
		ans = ans + a[i];
	}
	printf("%lld", ans);
	//system("pause");
	return 0;
}