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