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