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 $A$.

Input is given from Standard Input in the following format:

```
$N$
$B_1$ $B_2$ $...$ $B_{N-1}$
```

Print the maximum possible sum of the elements of $A$.

-   All values in input are integers.
-   $2 \leq N \leq 100$
-   $0 \leq B_i \leq 10^5$

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.