#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
char ans[1010][1010];
int main() {
	int h, w, x;
	cin >> h >> w >> x;
	bool bo = true;
	if (h % 4 == 3 && w % 4 == 3 && h != 3 && w != 3) {
		int now = h + w - 2;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if (j == 0 || i % 2 == 0) {
					ans[i][j] = '.';
				}
				else {
					ans[i][j] = '#';
				}
			}
		}
		for (int i = 0; i < h - 3; i += 4) {
			for (int j = 1; j < w; j += 2) {
				if (now < x) {
					ans[i + 1][j - 1] = '#';
					ans[i][j] = '.';
					ans[i][j + 1] = '.';
					ans[i + 1][j + 1] = '.';
					ans[i + 2][j + 1] = '.';
					ans[i + 2][j] = '.';
					now += 4;
				}
			}
		}
		if (now != x && (x - now) % 8 == 0) {
			for (int j = 1; j < w; j += 4) {
				if (now < x) {
					ans[h - 3][j] = '#';
					ans[h - 2][j + 1] = '.';
					ans[h - 1][j + 2] = '#';
					ans[h - 2][j + 3] = '.';
					now += 8;
				}
			}
		}
		else if (now != x) {
			cout << -1 << endl;
			return 0;
		}
		if (!bo) {
			for (int i = 0; i < w; i++) {
				for (int j = 0; j < h; j++) {
					cout << ans[j][i];
				}
				cout << endl;
			}
		}
		else {
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {
					cout << ans[i][j];
				}
				cout << endl;
			}
		}
		return 0;
	}
	if ((h > w & !w == 3) || h == 3 || h % 4 == 3) {
		swap(h, w);
		bo = false;
	}
	if (h + w - 2 <= x) {
		if ((h + w - 2) % 4 == x % 4) {
			int now = h + w - 2;
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {
					if (j == 0 || i % 2 == 0) {
						ans[i][j] = '.';
					}
					else {
						ans[i][j] = '#';
					}
				}
			}
			for (int i = 0; i < h - 3; i += 4) {
				for (int j = 1; j < w; j += 2) {
					if (now < x) {
						ans[i + 1][j - 1] = '#';
						ans[i][j] = '.';
						ans[i][j + 1] = '.';
						ans[i + 1][j + 1] = '.';
						ans[i + 2][j + 1] = '.';
						ans[i + 2][j] = '.';
						now += 4;
					}
				}
			}
			if (now != x) {
				cout << -1 << endl;
				return 0;
			}
			if (!bo) {
				for (int i = 0; i < w; i++) {
					for (int j = 0; j < h; j++) {
						cout << ans[j][i];
					}
					cout << endl;
				}
			}
			else {
				for (int i = 0; i < h; i++) {
					for (int j = 0; j < w; j++) {
						cout << ans[i][j];
					}
					cout << endl;
				}
			}
		}
		else {
			cout << -1 << endl;
		}
	}
	else {
		cout << -1 << endl;
	}
}