The natural numbers from 1 to 10 are each written on the blackboard 10 times. The student in the class than play the following game: a student deletes 2 of the numbers and instead of them writes down on the blackboard their sum decreased by 1;after that another student do the same; and so on. The game continues until only one number remains on the blackboard. The remaining number is:

a) Less than 440

b)451

c)460

d)488

e)more than 500