marks = int(input("enter your marks: "))

if marks>=80:
     grade = 'A+'
elif marks>=70:
     grade = 'A'
elif marks>60:
     grade = 'A-'
elif marks>50:
    grade = 'B+'
elif marks>40:
     grade = 'B'
else:
    grade = "F"

print("Your grade is", grade)