# Write your Python code here
for i in range(1, 6):
   marks = int(input("enter your marks: "))

   if(marks<=100 and marks>=90):
    grade = "Ex"
   elif(marks<90 and marks>=80) :
    grade = "A"   
   elif(marks<80 and marks>=70) :
    grade = "B"   
   elif(marks<70 and marks>=60) :
    grade = "C"   
   elif(marks<60 and marks>=50) :
    grade = "D"   
   elif(marks<50 ) :
    grade = "F" 

   print("your grade is : ", grade)