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