How much is it from 1 to 100? What's the formula?

How much is it from 1 to 100? What's the formula?

Formula, I don't know, but 1 + 2 + 3 + 4 + 5 + 6 +99 + 100 can be (1 + 99) + (2 + 98) + (3 + 97) (48 + 52) + (49 + 51) + 100 + 50, that is to say, there are 98 numbers of 100 and 50, and every two numbers add up to 100, which is 98 △ 2 = 49 (49 groups add up to 100), and there is another 100 and a 50. So the following is the algorithm, (98 △ 2) × 100 + 100 + 50 = 49 × 100 + 150 = 5000 + 150 = 5050. The following is the conversion (100 △ 2) × 100 + 50 = 50 × 100 + 50 = 5000 + 50 = 5050 according to the above formula