How to reshape a vector in a particular way

I got a column vector

a = [a1 a2 a3 ... an-1 an]'

and I wanna rearrange that in the following matrix

b = [a1 a2;a3 a4; ...; an-1 an]

like the first two pairs are the rows of the matrix, any tips on how achieve this?

Answer 1

[Azzi Abdelmalek]

b=reshape(a,2,[])'

[Carlos Lobato]

Thanks! Worked!