# Minimum Window Substring

Given two lowercase alphabet strings `a`

and `b`

, return the length of a minimum substring in `a`

that contains all the characters of `b`

.

If no such substring exists, return `-1`

.

**Constraints**

`0 ≤ n ≤ 100,000`

where`n`

is the length of`a`

`1 ≤ m ≤ 100,000`

where`m`

is the length of`b`

https://binarysearch.com/problems/Minimum-Window-Substring

## Examples

### Example 1

**Input**

- a =
`qthequickbrownfox`

- b =
`qown`

**Output**

- answer =
`10`

**Explanation**

The shortest substring that contains “qown” is “quickbrown” which has length of `10`

.

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