How to calculate 1+2+3+4+.........n

Hi friends!
Have you ever tried solving 1+2+3+4+.........n.
n stands for upto number.
So I am trying solving 1+2+3+4+.........1000.
There is a formula to calculate first n natural numbers.
The formula is:- n(n+1)/2
So according to formula I am going to put 1000 in the place of n.
1000(1000+1)/2
1000 X 1001/2
1001000/2
500500 Ans.
1+2+3+4+.......+1000 is equal to 500500.
Thanks