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();

		char[][] s = null;
		if (h % 4 == 3 && w % 4 == 3) {
			int max = h * (w / 2 + 1) + (w / 2) - 1;
			if (h % 4 == 3 && w % 4 == 3) {
				max -= Math.min(h, w) - 1;
			}
			if (x <= max) {
				s = solve(h, w, x);
			} else {
				if (h <= w) {
					int w2 = w - 2;
					max = h * (w2 / 2 + 1) + (w2 / 2) - 1;
					char[][] s1 = solve(h, w - 2, max);
					char[][] s2 = solve(h, 3, x - max + h - 1);
					if (s2 == null) {
						System.out.println(-1);
						return;
					}
					s = new char[h][w];
					for (int i = 0; i < h; i++) {
						for (int j = 0; j < w2; j++) {
							s[i][j] = s1[i][j];
						}
						for (int j = 0; j < 3; j++) {
							s[i][w2 - 1 + j] = s2[i][j];
						}
					}
				} else {
					int h2 = h - 2;
					max = w * (h2 / 2 + 1) + (h2 / 2) - 1;
					char[][] s1 = solve(h - 2, w, max);
					char[][] s2 = solve(3, w, x - max + w - 1);
					if (s2 == null) {
						System.out.println(-1);
						return;
					}
					s = new char[h][w];
					for (int j = 0; j < w; j++) {
						for (int i = 0; i < h2; i++) {
							s[i][j] = s1[i][j];
						}
						for (int i = 0; i < 3; i++) {
							s[h2 - 1 + i][j] = s2[i][j];
						}
					}
				}
			}
		} else {
			s = solve(h, w, x);
		}
		if (s == null) {
			System.out.println(-1);
			return;
		}

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

	static char[][] solve(int h, int w, int x) {
		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) {
			return null;
		}

		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);
		}
		return s;
	}

	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;
			}
		}
	}
}