$_ = <DATA>; $_ = $` if /$/; @a = split //, $_;

for $i (0 .. $#a){
   $e = $a[$i]; $hash{$e} = 1;
   for $y ($i+1 .. $#a){
                $e .= $a[$y]; $hash{$e} = 1;
   }
}

while(<DATA>){
   $_ = $` if /$/; @a = split //, $_; %thash = ();
   for $i (0 .. $#a){
        $e = $a[$i]; $thash{$e} = 1 if defined $hash{$e};
        for $y ($i+1 .. $#a){
                $e .= $a[$y]; $thash{$e} = 1 if defined $hash{$e};
        }
   }
   foreach $key (keys %hash){
        $hash{$key}++ if defined $thash{$key};
   }
}

$max = '';
foreach $key (keys %hash){
        if($hash{$key} == 3){
                $max = $key if length($max) < length($key);
        }
}

print "$max\n";

__DATA__
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