On the number axis, point A moves to the right 1 unit to get point B, and point B moves to the right (n+ 1)(n is a positive integer) to get point C. Points A, B and C represent rational numbers A, B and C respectively.

1 When n= 1, the positions of three points A, B and C on the number axis are as shown in the figure, and the product of the three numbers A, B and C is a positive number. If the sum of these three numbers is equal to one of them, then a=?

2 Move point C to the right by (n+2) units to get point D, which represents the product of rational numbers D, A, B, C and D is positive, the sum of these four numbers is equal to the sum of two of them, and A is an integer. If n takes 1, 2, 3, ..., 100, and the corresponding values of A are recorded as a 1, a2, a3, ..., respectively, then A 1+A2+A3+. +a 100=？