pk1,pk2,pk3,content
b,a,u,b-a-u
b,b,u,b-b-u
b,c,u,b-c-u
b,d,u,b-d-u
b,e,u,b-e-u
b,f,u,b-f-u
b,g,u,b-g-u
b,h,u,b-h-u
b,i,u,b-i-u
b,j,u,b-j-u
b,k,u,b-k-u
b,l,u,b-l-u