#!/usr/bin/perl
#

use strict;

my ($line, $num_divs, $count);

$num_divs = 0;
$count = 0;
while (<>) {
  chomp;
  $line = $_;

  if ($line =~ /Thread_Index/ && $count == 0) {
    $count = 100;
    last;
  }
  if ($line =~ /Mail Thread Index/ && $count == 0) {
    $count = 100;
    last;
  }

  if ($line =~ /^=+$/) {
    $num_divs++;
    next;
  }

  next if ($line =~ /^\s*$/);

  if ($num_divs == 3) {
    $count++;
  }

}

if ($count < 1) {
  print "yes\n";
}