Of the Greatest Common Divisor and the Universe

"If this (proving a question relating to the Greatest Common Divisor of two numbers) gets over your head and you don't understand it, which many of you will, do not worry. Take it home to your room of meditation tonight and ponder upon the wonders of the definition of the Greatest Common Divisor.
And in the morning, when you wake up and after you have pondered upon the wonders of the Universe, ponder upon the wonders of the definition of the Greatest Common Divisor."

MATH 135 Lecture by Steven Furino.