Algorithm to return the largest number without IF

On a job interview my friend had to solve this Problem:

Develop an algorithm that receives two variables, a and b both integer and returns the largest.

Example: If a = 7 and b = 7 the algorithm returns 7.

Restrictions:
- You can not use IF's not anything that comparison;
- Also one can not use Math or colections type libraries, because internally they use IF's;
- You can not use ternary operator, it is an IF.

It was the last question and at bottom of the page had the following sentence:

Do not look for perfection, just do the best you can.

We don't know if it's a hint or just a motivational phrase.

It is not mentioned or required a specific language, then i guess that can be used pseudocode or is a logic problem.

Here are several programmers, no one managed to solve.