use strict;
use warnings;

my %sequence;

while (my $seq = <DATA>) {
  if ($seq =~ /^(\w+)\s*=>\s*(\d+)/) {
    $sequence{$1} = $2 unless defined $sequence{$1} && $sequence{$1} > $2;
  }
}
for my $key (sort keys %sequence) {
  print "$key $sequence{$key}\n";
}

__DATA__
CIMG_00046 => 399
CIMG_00047 => 865
CIMG_00048 => 330
CIMG_00048 => 506
CIMG_00053 => 167
CIMG_00063 => 468
CIMG_00063 => 467
CIMG_00063 => 466
CIMG_00063 => 469
CIMG_00063 => 460
__END__

CIMG_00046 399
CIMG_00047 865
CIMG_00048 506
CIMG_00053 167
CIMG_00063 469