> #while (b<800)> <a*800+mod(b,800), a*800+mod(b+1,800), (a+1)*800+mod(b,800)>> <(a+1)*800+mod(b,800), (a+1)*800+mod(b+1,800), a*800+mod(b+1,800)>
Btw, since b is always smaller than 800, "mod(b,800)" is exactly
identical to just "b". (Where it does make a difference is in
"mod(b+1,800)".)
