use Math::BigInt;

my $N = Math::BigInt->new(shift @ARGV); 

while (1) {
  $N += 1;
  next unless prime($N);
  next unless prime($N+2);
  print "$N\n";
  exit;
} 

sub prime {
  my $n = shift;

  for (my $i = Math::BigInt->new(2); $i * $i <= $n; $i += 1) {
    return 0 if $n % $i == 0;
  }
  return 1;
}