r=x-p[x]?x=p[x],r:x
f='a[i]==a[x=i+d]&&(p[x=i,u=r]=r)==u'
p=({0..9999})
read w h
read -dx -aa
for((;d=i<w*h>y;y=~i%w&&f||(d=w,f),++i)){ :;}
im
echo ${_[y]}possible