// instead of computing the spiral and summing the diagonals, only get corners
fn main() {
    let dimension = 1001;
    let mut sum = 0;
    let squares = (dimension / 2) + 1;
    let mut last_square_end = 0;
    for square in 0..squares {
        if square == 0 {
            sum = 1;
            last_square_end = 1;
            continue;
        }
        for corner in 0..4 {
            sum += last_square_end + (square * 2) * (corner + 1);
        }
        last_square_end = last_square_end + (square * 2) * 4;
    }
    println!("{sum}");
}