This is a simple way to turn three numeric scores into a clear letter grade, like in a school grade book or learning platform. Write a function get_grade that takes s1, s2, and s3, calculates their average rounded down, and returns the matching letter. Use these ranges: A for 90–100, B for 80–89, C for 70–79, D for 60–69, and F for anything lower.

def get_grade(s1: int, s2: int, s3: int) -> str: