for i in range(8):
   id = input("Enter student ID: ")
   s1 = float(input("Enter first subject's mark: "))
   s2 = float(input("Enter second subject's mark: "))
   s3 = float(input("Enter third subject's mark: "))
   print("Student's ID: ", id)
   print("Average marks: "+"{:.2f}".format((s1+s2+s3)/3))