You are given an array of `n` strings `strs`, all of the same length.

We may choose any deletion indices, and we delete all the characters in those indices for each string.

For example, if we have `strs = ["abcdef","uvwxyz"]` and deletion indices `{0, 2, 3}`, then the final array after deletions is `["bef", "vyz"]`.

Suppose we chose a set of deletion indices `answer` such that after deletions, the final array has its elements in lexicographic order (i.e., `strs[0] <= strs[1] <= strs[2] <= ... <= strs[n - 1]`). Return the minimum possible value of `answer.length`.

Example 1:

    Input: strs = ["ca","bb","ac"]
    Output: 1
    Explanation:
    After deleting the first column, strs = ["a", "b", "c"].
    Now strs is in lexicographic order (ie. strs[0] <= strs[1] <= strs[2]).
    We require at least 1 deletion since initially strs was not in lexicographic order, so the answer is 1.

Example 2:

    Input: strs = ["xc","yb","za"]
    Output: 0
    Explanation:
    strs is already in lexicographic order, so we do not need to delete anything.
    Note that the rows of strs are not necessarily in lexicographic order:
    i.e., it is NOT necessarily true that (strs[0][0] <= strs[0][1] <= ...)

Example 3:

    Input: strs = ["zyx","wvu","tsr"]
    Output: 3
    Explanation: We have to delete every column.

Constraints:

- `n == strs.length`
- `1 <= n <= 100`
- `1 <= strs[i].length <= 100`
- `strs[i]` consists of lowercase English letters.