package Grains;

use strict;
use warnings;
use feature qw<say>;
use bignum;

use Exporter qw<import>;
our @EXPORT_OK = qw<grains_on_square total_grains>;

sub grains_on_square {
    my ($square) = @_;
    die "square must be between 1 and 64"
        if $square < 1 or $square > 64;
    return 2 ** ( $square - 1 );
}

sub total_grains {
    my $total;
    foreach my $square ( 1 .. 64 ) {
        $total += grains_on_square( $square );
    }
    return $total;
}

1;