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#!/usr/bin/perl
use strict;
use warnings;
sub cycle_length {
my ($n) = @_;
my $carry = 1;
my $idx = 0;
my %seen;
for my $i (1..$n) {
$carry = ($carry * 10) % $n;
return $idx - $seen{$carry} if exists $seen{$carry};
$seen{$carry} = $idx++;
}
die "oops! ($n)";
}
my ($max, $max_idx) = (0, 0);
for (2..1000) {
my $length = cycle_length($_);
if ($length > $max) {
$max = $length;
$max_idx = $_;
}
}
print "$max_idx\n";
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