According to Gauss, the formula to find the sum of a series is:
S=n(n+1)/2 where n is the number of terms in the series
Since n=2000, then:
S=2000(2000+1)/2
S=4002000/2
S=2001000
The famous mathematician Gauss had used this same method to find the sum of the digits 1 to 100 while in elementary school. So the sum of the first 2000 positive integers is 2,001,000
