When n = 1, s = (1- 1)/2.

n=2，s =( 1- 1)/2+(2- 1)/2

n=3，s =( 1- 1)/2+(2- 1)/2+(3- 1)/2； ........n=20 15，s=...+(20 15- 1)/2

When n=20 16, S will be output.

Therefore, s = (1-1)/2+(2-1)/2+...+(2015-1)/2.

=( 1+2+3+...+20 14)/2=(

( 1+20 14)*20 14/2

)/2

= 10 14552.5

The final output is S= 10 14552.5.