how to find the greatest no of n given numbers using c#

Question

hi , i have 6 asp.net webpages, for them i calculate the time spent on each webpage by user by using ajax timer in every page
and i put the timespent in seconds in session when user clicks signout
i have to calculate greatest timespent among all these which are in every page session object
so help me on this , how to calculate the gratest no of given n numbers using asp.net c#