# Challenge 55 - Score to Badge Function
def badge_for(score):
    if not isinstance(score, int) or not 0 <= score <= 100:
        return "Invalid score"
    if score < 40:
        return "Starter"
    if score < 70:
        return "Builder"
    if score < 90:
        return "Developer"
    return "Expert"

for score in (0, 39, 40, 70, 90, 100):
    print(f"{score}: {badge_for(score)}")