Erdős number

Erdős number is a measure of how close a person is to the famous mathematician Paul Erdős. If someone worked directly with Paul Erdős on a math project, then they would have an Erdős number of 1. If someone worked with someone who worked directly with Erdős, then they would have an Erdős number of 2 and so on. The number can go up to any number, but most people have an Erdős number of 4 or less.