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