#!/usr/bin/perl

# http://perlmonks.org/?node_id=1211497

use strict;
use warnings;

sub up
  {
  my ($row, $col) = split /-/, $_[0];
  return $_[0] eq '0-0' ? "@_\n" :
    ($row * $col > 0 && up( ~-$row . '-' . ~-$col, @_ ) ) .
      ($row > $col && up( ~-$row . '-' . $col, @_ ) );
  }

print up( '3-1' );