fn main() {
    let n = 20;
    for i in 0..n {
        for j in 0..n {
            print!(
                "{:2}",
                if i == 0 || i == n - 1 || j == 0 || j == n - 1 || i == j || i + j == n - 1 {
                    "▉"
                } else {
                    " "
                }
            );
        }
        println!();
    }
}