I know that the sum of the first n counting numbers is n(n+1)/2, so I can use that formula to find the sum of the first 102 counting numbers. Plugging in n = 102, I get 102(103)/2, which is 5253. Now I need to find the remainder when 5253 is divided by 5250. I notice that 5253 is just 3 more than 5250, so the remainder must be 3. 
What is the remainder when the sum of the first 102 counting numbers is divided by 5250?  (The first counting number is 1.)