#!/usr/bin/env perl

use strict;
use warnings;
use v5.22;
use List::Util qw( max );

sub draw_matrix {
    my ($matrix) = shift;
    my $answer;
    foreach my $y (@$matrix) {
        foreach my $x (@$y) {
            $answer++ if (defined( $x) && ($x > 1));
        }
    }
    return $answer;
}

if (@ARGV !=1) {
    die "Usage: $0 [input-filename]";
}

my $input_filename = $ARGV[0];
open my $filehandle, '<', $input_filename or
    die "Could not open input file $input_filename: $!";

chomp( my @input = ( <$filehandle> ) );
my $wait;
my @matrix = ();
my ($rows, $columns) = (0, 0);
foreach (@input) {
    my ($x1, $y1, $x2, $y2) = ( /(\d+),(\d+) -> (\d+),(\d+)/ );
    if ($x1 == $x2) { # line is vertical
        ($y1, $y2) = ($y2, $y1) if ($y1 > $y2); # swap so that $y1 < $y2
        for (my $y = $y1; $y <= $y2; $y++) {
            $matrix[$y][$x1]++;
        }
    }
    elsif ($y1 == $y2) { # line is horizontal
        ($x1, $x2) = ($x2, $x1) if ($x1 > $x2); # swap so that $x1 < $x2
        for (my $x = $x1; $x <= $x2; $x++) {
            $matrix[$y1][$x]++;
        }
    }
    else { # line is diagonal
        my $dx = ($x2 > $x1) ? 1 : -1;
        my $dy = ($y2 > $y1) ? 1 : -1;
        for (my $x = $x1, my $y = $y1; $x!=$x2 && $y!=$y2; $x+=$dx, $y+=$dy) {
            $matrix[$y][$x]++;
        }
        $matrix[$y2][$x2]++; # for loop above stops just before reaching 2nd point
    }
}

say draw_matrix( \@matrix );