use strict;
use warnings;

my @nums = split '', <>;
my $n = $#nums+1;

my @dp;
for my $i (0..(1<<$n)-1){
  $dp[$i] = [0, $n];
}

my(@nd, $val, @pos);
my @ans = (0);
for my $d (0..(1<<$n)-1){
  next if($dp[$d][1] < 3);

  for my $i (0..$n-1){
    next if(($d>>$i) % 2);
    $nd[0] = $d | 1<<$i;
    $dp[$nd[0]][1] = $dp[$d][1]-1;
    if($i < $n-1-1){
      for my $j ($i+1..$n-1){
        next if(($nd[0]>>$j) % 2);
        $nd[1] = $nd[0] | 1<<$j;
        $dp[$nd[1]][1] = $dp[$nd[0]][1]-1;
        if($j < $n-1){
          for my $k ($j+1..$n-1){
          next if(($nd[1]>>$k) % 2);
            $nd[2] = $nd[1] | 1<<$k;
            $dp[$nd[2]][1] = $dp[$nd[1]][1]-1;
            @pos = map {$n-1 - $_} ($i, $j, $k);
            if(0 < $nums[$pos[2]] and $nums[$pos[2]] != $nums[$pos[1]] and $nums[$pos[1]] == $nums[$pos[0]]){
              $val = $nums[$pos[2]].$nums[$pos[1]].$nums[$pos[0]] + $dp[$d][0];
              if($dp[$nd[2]][0] < $val){
                $dp[$nd[2]][0] = $val;
                push @ans, $val;
              }
            }
          }
        }
      }
    }
  }
}

print+(sort {$b <=> $a} @ans)[0];