Description

To help Baitesa! The rings on the chain are numbered $1, 2, \ldots, n$. We can detach them according to the following rules:

• At each step, you may attach or detach exactly one ring to or from the fence.
• Ring $1$ can always be attached or detached.
• If rings $1, \ldots, k - 1$ are all detached and ring $k$ is attached, where $1 \le k < n$, then you may attach or detach ring $k + 1$.

Write a program that, given the description of the Byte Chain, computes the minimum number of operations needed to remove all rings from the fence and outputs the result.

Input Format

The first line contains an integer $n$, where $1 \le n \le 1000$.
The second line contains $n$ integers $o_1, o_2, \ldots, o_n$ (each is $0$ or $1$) separated by single spaces. If $o_i = 1$, then the $i$-th ring is attached to the fence; if $o_i = 0$, then the $i$-th ring is not attached.

Output Format

Output a single integer: the minimum number of operations required to detach all rings from the fence.

4
1 0 1 0

6

Hint

Translated by ChatGPT 5