while True: try: marks = int(input("Enter your marks 0 to 100 to see your grade: ")) except ValueError: print('Invalid input, try again') continue else: break if marks > 100: print('Invalid marks') elif marks > 90 < 100: print('Grade A') elif marks > 80 <= 90: print('Grade B') elif marks >= 60 <= 80: print('Grade C') elif marks < 60: print('Grade D') else: print('You have failed')