use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let h: usize = itr.next().unwrap().parse().unwrap();
    let w: usize = itr.next().unwrap().parse().unwrap();
    let x: usize = itr.next().unwrap().parse().unwrap();

    let mn = h + w - 2;
    let mx = (h + 1) / 2 * (w - 1) + h - 1;
    // println!("{} {}", mn, mx);
    if mn <= x && x <= mx && (mx - x) % 4 == 0 {
        let mut g = vec![vec!['.'; w]; h];
        for i in 0..h {
            if i % 2 == 1 {
                for j in 0..w {
                    g[i][j] = '#';
                }
            }
        }
        let mut dec = (mx - x) / 4;
        for i in 0..h {
            if (i + 1) % 4 == 0 {
                let dec_max = w / 2;
                if dec_max <= dec {
                    g[i][w - 1] = '.';
                    dec -= dec_max;
                } else {
                    g[i][dec * 2] = '.';
                }
            } else if (i + 1) % 2 == 0 {
                g[i][w - 1] = '.';
            }
        }
        for i in 0..h {
            for j in 0..w {
                print!("{}", g[i][j]);
            }
            println!("");
        }
    } else {
        println!("-1");
    }
}