pk1,pk2,pk3,content
a,x,a,a-x-a
a,x,b,a-x-b
a,x,c,a-x-c
a,x,d,a-x-d
a,x,e,a-x-e
a,x,f,a-x-f
a,x,g,a-x-g
a,x,h,a-x-h
a,x,i,a-x-i
a,x,j,a-x-j
a,x,k,a-x-k
a,x,l,a-x-l
a,x,m,a-x-m
a,x,n,a-x-n
a,x,o,a-x-o
a,x,p,a-x-p
a,x,q,a-x-q
a,x,r,a-x-r
a,x,s,a-x-s
a,x,t,a-x-t
a,x,u,a-x-u
a,x,v,a-x-v
a,x,w,a-x-w
a,x,x,a-x-x
a,x,y,a-x-y
a,x,z,a-x-z