import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int h = sc.nextInt();
		int w = sc.nextInt();
		int x = sc.nextInt();
		sc.close();

		int min = h + w - 2;
		int max = h * (w / 2 + 1) + (w / 2) - 1;
		if (h % 4 == 3 && w % 4 == 3) {
			max -= Math.min(h, w) - 1;
		}
		int y = max - x;
		if (x < min || max < x || y % 4 != 0) {
			System.out.println(-1);
			return;
		}

		y /= 4;
		char[][] s = new char[h][w];
		for (int i = 0; i < h; i++) {
			Arrays.fill(s[i], '.');
		}
		for (int i = 1; i < h; i += 2) {
			for (int j = 1; j < w; j += 2) {
				s[i][j] = '#';
			}
		}

		boolean tate = true;
		if (w % 4 == 3) {
			if (h % 4 == 1 || h > w) {
				tate = false;
			}
		}
		if (tate) {
			tate(s, h, w, y);
		} else {
			yoko(s, h, w, y);
		}

		PrintWriter pw = new PrintWriter(System.out);
		for (int i = 0; i < h; i++) {
			pw.println(s[i]);
		}
		pw.flush();
	}

	static void tate(char[][] s, int h, int w, int y) {
		for (int j = 1; j < w; j += 4) {
			s[0][j] = '#';
		}
		for (int i = 2; i < h - 1; i += 2) {
			for (int j = 1; j < w; j += 2) {
				s[i][j] = '#';
			}
		}
		for (int j = 3; j < w; j += 4) {
			s[h - 1][j] = '#';
		}

		int i = h - 1;
		int j = 1;
		for (int k = 0; k < y; k++) {
			s[i][j] = '#';
			s[i - 2][j] = '.';
			i -= 2;
			if (i < 2) {
				i = h - 1;
				j += 4;
			}
		}
	}

	static void yoko(char[][] s, int h, int w, int y) {
		for (int i = 1; i < h; i += 4) {
			s[i][0] = '#';
		}
		for (int j = 2; j < w - 1; j += 2) {
			for (int i = 1; i < h; i += 2) {
				s[i][j] = '#';
			}
		}
		for (int i = 3; i < h; i += 4) {
			s[i][w - 1] = '#';
		}

		int j = w - 1;
		int i = 1;
		for (int k = 0; k < y; k++) {
			s[i][j] = '#';
			s[i][j - 2] = '.';
			j -= 2;
			if (j < 2) {
				j = w - 1;
				i += 4;
			}
		}
	}
}