i:.''" -> "\'0:"i/14"
m:1000 1000#0
cords:,/{,/(1_&':x)+/:'{$[*x;(!1+*x),'x[1];(*x),'!1+x[1]]}'1_(|/-:\-)':x}'i
bot:2+|/*'|'cords
m:|/{.[m;|x;:;1]}'cords
m[bot;]:1
step:{t:m[1+x[1];x[0]+0 -1 1];$[&/t;x;x+(0 -1 1@*&~t),1]}
{~|/m[bot-1]}{p:step/500 0; m[*|p;*p]:2}/m;
-1++//2=m
{p:step/500 0; m[*|p;*p]:2; m}/m;
+//2=m