$"='';
@M=(0)x(@N=<>=~/./g);
for($k=0;2*$k<=@N-10;++$k){
	@M[$k,$k+9,$#N-$k,@N-10-$k]=($|?9:$N[$k])x4;
	@M[$k,$k+9,$#N-$k,@N-10-$k]=($N[$k]-1)x4,$|=1if"@M">"@N"
}
$%="@M[0..(@N-10)/2]"+1if$M[0]--;
$%+=9*10**($_>>1)for 0..@N-11;
print$%,$/