CF2260A.Monocarp's Contest

Monocarp is preparing a team programming contest. The contest has $n$ problems, each of which is either easy or hard. The problems are numbered from $1$ to $n$.

Monocarp wants the first and the last problems of the contest to be easy. In one operation, he can choose any two problems and swap them.

Determine the minimum number of operations required to make the first and the last problems easy, or report that it is impossible.

Monocarp 正在筹备一场团队编程竞赛。该竞赛共有 $n$ 道题目，每道题要么是简单题，要么是难题。题目编号从 $1$ 到 $n$。

Monocarp 希望竞赛的第一题和最后一题均为简单题。在一次操作中，他可以任选两道题并交换它们的位置。

请确定使第一题和最后一题均为简单题所需的最少操作次数；若不可能实现，请报告这一点。

The first line contains an integer $t$ ($1 \le t \le 10^3$) — the number of test cases.

Each test case consists of two lines

• the first line contains one integer $n$ ($2 \le n \le 50$) — the number of problems in the contest;
• the second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($0 \le a_i \le 1$). If $a_i=0$, then the problem with number $i$ is easy; if $a_i=1$, then it is hard.

第一行包含一个整数 $t$（$1 \le t \le 10^3$）—— 测试用例的数量。

每个测试用例由两行组成：

• 第一行包含一个整数 $n$（$2 \le n \le 50$）—— 比赛中问题的数量；
• 第二行包含 $n$ 个整数 $a_1, a_2, \ldots, a_n$（$0 \le a_i \le 1$）。若 $a_i=0$，则编号为 $i$ 的问题为简单题；若 $a_i=1$，则该题为难题。

For each test case, print the minimum number of operations required to make the first and the last problems easy. If it is impossible to satisfy the requirement, print $-1$.

对于每个测试用例，输出使第一个和最后一个题目变为简单题所需的最少操作次数。如果无法满足该要求，则输出 $-1$。

In the first test case, the first and the last problems are already easy, so no operations are needed.

In the second test case, there is only one easy problem, so it is impossible to make both the first and the last problems easy.

In the third test case, one can swap the first and the second problems.

In the fourth test case, one can first swap the first and the second problems, and then — the third and the fifth problems.

在第一个测试用例中，第一题和最后一题已经是简单题，因此无需任何操作。

在第二个测试用例中，仅有一道简单题，因此无法使第一题和最后一题同时变为简单题。

在第三个测试用例中，可以交换第一题和第二题。

在第四个测试用例中，可以先交换第一题和第二题，再交换第三题和第五题。