h, w, x = map(int, input().split()) r = x - (h - 1) - (w - 1) if r < 0 or r % 4: print(-1) exit() r //= 4 s = [[(i | j) & 1 for j in range(w)] for i in range(h)] for i in range(h): s[i][0] = 0 for j in range(w): s[h-1][j] = 0 di = [1, 0, -1, 0] dj = [0, 1, 0, -1] def flip(i, j): for k in range(4): ni = i + di[k] nj = j + dj[k] s[ni][nj] ^= 1 i = h - 2 j = w - 2 if j == 1: i -= 2 while r and i > 0 and j > 0: r -= 1 flip(i, j) if j == 1: i -= 4 else: i -= 2 if i < 0: j -= 4 i = h - 2 if j == 1: i -= 2 if r != 0: print(-1) exit() for si in s: print(''.join('.#'[x] for x in si))