$1=0
while($1+$2<H*W)
$2=$2+(A[$1/W+1,$1%W+1]-B[$1/W+1, $1%W+1])*(A[$1/W+1,$1%W+1]-B[$1/W+1,$1%W+1])*H*W
$1=$1+1
end
$1=$1-1
return($1/W+1,$1%W+1)