Mock Canadian Computing Competition: 2026 Senior #2

The quick brown fox jumps over the lazy dog is a famous sentence that contains all the letters of the English alphabet from a to z. Such a sentence or phrase that have all the letters in the alphabet appear at least once is known as a pangram.

Amelia has a set of ~S~ strings, each containing only lowercase alphabetical letters, each with a length of ~L~. She would like to put as many as of them as she can in a bag such that all the strings combined within the bag form a pangram. Unfortunately, the bag can only fit exactly ~S-1~ strings, and so she must choose one to exclude from being within the bag.

For example, if she has the following ~3~ strings:

• abcdefghijklmnopqrstuvwxxy
• abcdefghijklmnopqrstuvwyyz
• abcdefghijklmnopqrstuvwzzz

Amelia could choose to remove either the ~2^\text{nd}~ or ~3^\text{rd}~ string, and the remaining ~2~ would form a pangram. However, if she removed the ~1^\text{st}~ string, then the remaining letters would not form a pangram since the letter x would not appear in the remaining strings. In this case, she has ~2~ choices of strings that she could remove such that the remaining strings form a pangram.

How many of her ~S~ strings can she exclude such that the remaining ~S-1~ strings form a pangram?

Input Specification

The first line contains ~2~ spaced integers ~S~ and ~L~, indicating the number of strings and the length of the strings respectively.

The next ~S~ lines each contain a string of ~L~ lowercase alphabetical characters.

The following table shows how the available 15 marks are distributed.

Marks	Bounds on ~S~	Bounds on ~L~
~3~ marks	~1 \le S \le 100~	~1 \le L \le 100~
~5~ marks	~1 \le S \le 1\,000~	~1 \le L \le 1\,000~
~7~ marks	~1 \le S \le 10\,000~	~1 \le L \le 1\,000~

Output Specification

Output the number of strings that she could exclude from her set of ~S~ strings, such that the remaining ones form a pangram.

Sample Input 1

3 26
abcdefghijklmnopqrstuvwxxy
abcdefghijklmnopqrstuvwyyz
abcdefghijklmnopqrstuvwzzz

Output for Sample Input 1

2

Explanation of Output for Sample Input 1

This is the case from the problem statement.

Sample Input 2

2 1
a
b

Output for Sample Input 2

0

Explanation of Output for Sample Input 2

There is no way to exclude one string such that the other one is a pangram.

Sample Input 3

8 5
yxwvu
tsrqp
onmlk
jihgf
edcba
tnalp
osmqz
rkpzp

Output for Sample Input 3

5

Explanation of Output for Sample Input 3

Amelia could choose to exclude either the ~2^\text{nd}~, ~3^\text{rd}~, ~6^\text{th}~, ~7^\text{th}~, or ~8^\text{th}~ string.