import sys

h, w, k = map(int, sys.stdin.buffer.read().split())
if k and (((h == 1 or w == 1) and k != 1) or (h > 1 and w > 1 and not 2 <= k <= h * w - h - w + 2)):
    print(-1)
    raise SystemExit
transpose = h > w
if transpose:
    h, w = w, h
grid = [["."] * w for _ in range(h)]
if k == 0:
    grid = [["#"] * w for _ in range(h)]
elif h == 1:
    grid[0][0] = "#"
elif k <= w:
    grid[0][:k - 1] = ["#"] * (k - 1)
else:
    extra, columns, cap = k - w, list(range(0, w, 2)), h - 2
    one = [i for i, c in enumerate(columns) if c == 0 or c == w - 1]
    two = [i for i, c in enumerate(columns) if c != 0 and c != w - 1]
    low, high = max(0, extra - 2 * cap * len(two)), min(cap * len(one), extra)
    ones = next(x for x in range(low, high + 1) if x % 2 == extra % 2)
    lengths, remain = [1] * len(columns), ones
    for i in one:
        take = min(cap, remain)
        lengths[i] += take
        remain -= take
    remain = (extra - ones) // 2
    for i in two:
        take = min(cap, remain)
        lengths[i] += take
        remain -= take
    grid[0][:columns[-1] + 1] = ["#"] * (columns[-1] + 1)
    for i, c in enumerate(columns):
        for r in range(lengths[i]):
            grid[r][c] = "#"
if transpose:
    grid = [list(row) for row in zip(*grid)]
print("\n".join(map("".join, grid)))