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#!/usr/bin/perl
use 5.016; # implies strict, provides 'say'
use warnings;
use autodie;
use List::Util qw/sum/;
use Data::Dumper;
use EulerHelper;
# Starting with the number 1 and moving to the right in a clockwise
# direction a 5 by 5 spiral is formed as follows:
# 21 22 23 24 25
# 20 7 8 9 10
# 19 6 1 2 11
# 18 5 4 3 12
# 17 16 15 14 13
# It can be verified that the sum of the numbers on the diagonals is 101.
# What is the sum of the numbers on the diagonals in a 1001 by 1001
# spiral formed in the same way?
### CODE
# top right= n*n
# bottom right = n*n - n +1
# bottom left = n*n-2*n+2
# top left = n*n-3*n+3
# total = 4*n*n - 6*n + 6
my $total = 1;
for ( my $n = 3 ; $n <= 1001 ; $n += 2 ) {
$total += 4 * $n * $n - 6 * $n + 6;
}
say $total;