#Calculate grade of the student from marks

marks = int(input("Enter your marks\n"))

if marks>90:
    grade = "Ex"
elif marks>=80:
    grade = "A"
elif marks>=70:
    grade = "B"
elif marks>=60:
    grade = "C"
elif marks>=50:
    grade = "D"
else:
    grade = "F"

print("Your grade is "+ grade)