Given an array of **0** and **1**. In how many iterations it is possible that the whole array can be filled with 1's, if in a single iteration immediate neighbours of 1's can be filled.

**Input:**

The first line contains a single integer **T**, the number of test cases. The first line consists of a single integer **N**(length of array). The next line consists of a N spaced integers(either 0 or 1).

**Output:**

For each testcase, print the minimum number of iterations to fill the whole array with 1's (if possible). If it is not possible to fill the array with 1s, print "-1" (without quotes).

**Constraints:**

1 <= T <= 10^{3}

1 <= N <= 10^{7}

0 <= A_{i }<= 1

**Examples:**

**Input:**

2

4

1 0 1 0

17

0 0 1 1 0 0 1 1 0 1 1 1 1 0 0 0 1

**Output:**

1

2

**Explanation:**

**Test Case 1:** Both the 0s has 1 as their immediate neighbour. So, we only need one iteration to fill the array with 1.

Author: saksham0751

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