#!/usr/bin/perl

#Thanks to Mike Muuss for the math ;)

$num=0;
$tsumsq=0;
$tsum=0;
$ded=0;

$thresmul=4.0;

while(<>){
	chomp;
	($x, $y)=split;
	if($y ne "??"){
	   push @dat, [ $x, $y ];
	   $num++;
	   $tsum+=$y;
	   $tsumsq+=($y*$y);
	}
	else {
	   push @dat, [ $x, $y ];
	   $ded++;
	}
}

$avg=$tsum / $num;
$dev=sqrt($tsumsq / $num - $avg * $avg); 
$thresh= $dev * $thresmul;

for($j=0; $j<($num+$ded); $j++){
	if($dat[$j][1] ne "??"){
		if(abs($dat[$j][1] - $avg) > $thresh){
		  $dat[$j][1]="??";
   		}
	}
   print $dat[$j][0], " ", $dat[$j][1], "\n";
}