# https://github.com/tyuyu-62/cp-library
from collections import deque, defaultdict
from itertools import permutations, product
from bisect import bisect_left, bisect_right
from heapq import heappush, heappop
from random import randint, shuffle
from time import perf_counter as pc
def II(): return int(input())
def LI(dec=0): return [int(x) - dec for x in input().split()]
def SI(): return input()
def LS(): return list(input().split())
mod = 998244353
inf = 2002002002002002002

import sys
sys.setrecursionlimit(10 ** 6)
input = lambda: sys.stdin.readline().rstrip()
_buf = []
def print(*args, sep=" "): _buf.append(sep.join(map(str, args)))
def debug(*args):
    if DEBUG: sys.stdout.write(" ".join(map(str, args)) + "\n")
DEBUG = True

def solve():
    H, W, K = LI()
    KK = K
    def check(A):
        cnt = 0
        for i in range(H - 1):
            for j in range(W):
                cnt += A[i][j] != A[i + 1][j]
        for i in range(H):
            for j in range(W - 1):
                cnt += A[i][j] != A[i][j + 1]
        return cnt == KK
    if H == 1 or W == 1:
        mx = max(H, W)
        A = ["."] * mx
        for j in range((K + 1) & 1, K, 2):
            A[j] = "#"
        if H == mx:
            A = [[A[i]] for i in range(H)]
        else:
            A = [A]
        # assert check(A)
        for ai in A:
            print("".join(ai))
    elif K == 1 or K == 2 * H * W - H - W - 1:
        print(-1)
    elif H == 2 or W == 2:
        K = 2 * H * W - H - W - K
        mx = max(H, W)
        mn = min(H, W)
        A = [["." for _ in range(mx)] for _ in range(mn)]
        if K % 3 == 1:
            A[0][0] = A[(mx - 1) & 1][-1] = "#"
            K -= 4
        elif K % 3 == 2:
            A[0][0] = "#"
            K -= 2
        K = K // 3
        for i in range(1, 1 + K):
            A[i & 1][i] = "#"
        if H == mx:
            A = [[A[j][i] for j in range(mn)] for i in range(mx)]
        for i in range(H):
            for j in range(W):
                if (i + j) & 1: continue
                if A[i][j] == "#":
                    A[i][j] = "."
                else:
                    A[i][j] = "#"
        # assert check(A)
        for ai in A:
            print("".join(ai))
    elif H == W == 3:
        if K == 0:
            A = ["...", "...", "..."]
        elif K == 2:
            A = ["...", "...", "..#"]
        elif K == 3:
            A = ["...", "...", ".#."]
        elif K == 4:
            A = ["...", "...", "#.#"]
        elif K == 5:
            A = ["...", "#..", "..#"]
        elif K == 6:
            A = ["...", "#.#", "..."]
        elif K == 7:
            A = [".#.", "...", "#.#"]
        elif K == 8:
            A = ["#.#", "...", "#.#"]
        elif K == 9:
            A = ["...", "#.#", ".#."]
        elif K == 10:
            A = ["#.#", ".#.", "#.."]
        else:
            A = [".#.", "#.#", ".#."]
        # check(A)
        for ai in A:
            print("".join(ai))
    else:
        mx = max(H, W)
        mn = min(H, W)
        A = [[0] * mn for _ in range(mx)]
        L = (K - 2) // 4
        for i in range(1, mx - 1):
            for j in range(1, mn - 1):
                if (i + j) & 1 == 0:
                    if L:
                        L -= 1
                        K -= 4
                        A[i][j] = 1
        q, r = divmod(K, 3)
        L = (H - 1) // 2 * 2 + (W - 1) // 2 * 2
        if r == 1:
            q -= 1
        for i in range(1, mx - 1):
            for j in [0, mn - 1]:
                if (i + j) & 1 == 0:
                    if L:
                        L -= 1
                        K -= 3
                        A[i][j] = 1
        for i in [0, mx - 1]:
            for j in range(1, mn - 1):
                if (i + j) & 1 == 0:
                    if L:
                        L -= 1
                        K -= 3
                        A[i][j] = 1
        for i in [0, mx - 1]:
            for j in [0, mn - 1]:
                if (i + j) & 1 == 0:
                    if K:
                        K -= 2
                        A[i][j] = 1
        A = [[".#"[(A[i][j] ^ (i + j)) & 1] for j in range(mn)] for i in range(mx)]
        if H == mn:
            A = [[A[j][i] for j in range(mx)] for i in range(mn)]
        # check(A)
        for ai in A:
            print("".join(ai))
    return

if __name__ == "__main__":
    T = 1
    # T = II()
    for _ in range(T):
        solve()
    sys.stdout.write("\n".join(_buf) + "\n")