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