In mathematics, a perfect number refers to a number where the sum of its divisors, excluding the number itself, equals the number.

He is immersed in the study of panmagic squares.

This fish is completely farmed, and no capture is done in the natural environment.

He likes to take a walk in the park at dusk.

He is a perfectionist, so he is very strict about his work.

He played a perfect fifth scale on the piano.

We should always remember the power of Kannon in difficult times.

This ancient proverb, 'know the other side and yourself, and you will not be in danger in a hundred battles', teaches us the importance of understanding ourselves and others.