# Minimum Number of Contiguous K-Flips

You are given a list of integers `nums`

containing `1`

s and `0`

s and an integer `k`

. Consider an operation where we flip a sublist of length `k`

such that all `1`

s become `0`

s and all `0`

s become `1`

s.

Return the minimum number of operations required to turn `nums`

into all `0`

s. If it’s not possible return `-1`

.

**Constraints**

`k ≤ n ≤ 100,000`

where`n`

is the length of`nums`

.

https://binarysearch.com/problems/Minimum-Number-of-Contiguous-K-Flips

## Examples

### Example 1

**Input**

- nums =
`[1, 1, 1]`

- k =
`2`

**Output**

- answer =
`-1`

**Explanation**

There’s no way to flip the numbers such that they all become `0`

s.

### Example 2

**Input**

- nums =
`[1, 1, 0, 1, 1]`

- k =
`2`

**Output**

- answer =
`2`

**Explanation**

We can flip the first two numbers to zero and then flip the last two numbers to zero.

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