#!/usr/bin/perl

$filename = "15.txt";

open(FILE, $filename);
@data = <FILE>;
close(FILE);

$input = $data[0];
$input =~ s/[^0-9,]*//sgi;

%firstspoke = ();

@init = split(",",$input);

$turn = 1;

foreach $ini (@init) {
    $firstspoke{$ini} = $turn;
    $lastspoken = $ini;
    $turn++;
}


for ($i = $turn; $i < 30000001; $i++) {

    if (int($firstspoke{$lastspoken}) > 0) {
         $diff = ($i - 1) - int($firstspoke{$lastspoken});
    }
    else
    {
           $diff = 0;
    }

    $firstspoke{$lastspoken} = ($i - 1);
    $lastspoken = $diff;

    if ($i == 2020) {
    print "P1: $lastspoken\n";
    }

}

print "P2: $lastspoken\n";