#!/usr/bin/env perl

use strict;
use warnings;

my ($x, $y) = split / /,<>; chomp $y;
my $n = <>; chomp $n;
if ($n <= 2) {
  print "YES\n";
  exit;
}
my @arr = split/ /,<>; chomp $arr[@arr - 1];
unshift @arr, 0;
$n++;
my $ratio = $y / $x;
my ($xsum, $ysum) = (0, 0);
for (my $i = 0; $i < $n - 2; $i++) {
  my $base = $arr[$i + 1] - $arr[$i];
  $xsum += $base;
  $ysum += $base * $ratio;
  my $nex = $arr[$i + 2] - $arr[$i + 1];
  if ($ysum - $xsum > $nex) {
    print "NO\n";
    exit;
  }
}
print "YES\n";