You are given :

• A list of spam words
• A list of email subjects

An email is classified as spam if:

• Repeated spam words count individually (e.g., 'free free' counts as 2)
• Its subject contains at least two spam words
• Matching is not case-sensitive

For each subject, return:

• 'not_spam' otherwise
• 'spam' if it contains 2 or more spam words

Example

Suppose subjects = ['free prize worth millions', 'ten tips for a carefree lifestyle'], and spamWords = ['free', 'money', 'win', 'millions'].

Output: ['spam', 'not_spam']

Explanation:

• 'free prize worth millions' contains 'free' and 'millions' (2 spam words) -> 'spam'
• 'ten tips for a carefree lifestyle' contains no spam words -> 'not_spam'