def isBig(val):
    if val >= 1000:
        print str(val) + " IS big!!!"
    else:
        print str(val) + " is NOT big!"

def lettergrade(grade):
    if grade >= 90:
	return 'A'
    elif grade >= 80:
	return 'B'
    elif grade >= 70:
	return 'C'
    else:
        return 'NC'