Computing to infinity

What is the sum to infinity?

S= 1+ (-1) + 1+ (-1) + (-1) + (-1) + (-1) + 1 + ….

Answer:   This is an excellent example of associativity for addition:

S = (1 + -1) + (1 + -1) + (1 + -1) ……

S = 0 + 0 + 0 +….

S = 0

However

S= 1 + (-1 +1) + (-1 +1) + (-1 +1) + ……….

S = 1 + 0 + 0 + 0 + …………..

S= 1

However, if s= 0 and 1 then 2S = 1 and ½

Thus the sum is indeterminate.