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-----
3
2 5

-----Sample Output-----
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.

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