def solve1(h, w, x):
  if (x-(h-1)-(w-1))%4 != 0:
    return ["-1"]
  if not (h-1)+(w-1) <= x <= ((h//2+1)*(w//2+1)-1)*2:
    return ["-1"]
  ans = [["#"]*w for i in range(h)]
  for i in range(0, h, 2):
    ans[i] = ["."]*w
  for i in range(1, h, 4):
    ans[i][w-1] = "."
  x -= (h-1)+(w-1)
  for i in range(3, h, 4):
    y = min(x//2, w-1)
    ans[i][(w-1)-y] = "."
    x -= y*2
  return ans

def solve2(h, w, x):
  if (x-(h-1)-(w-1))%4 != 0:
    return ["-1"]
  if not (h-1)+(w-1) <= x <= ((h//2+1)*(w//2+1)-2)*2:
    return ["-1"]
  ans = [["#"]*w for i in range(h)]

  if (h-3)+(2*(w//2+1)-2)*2 <= x:
    ans[0][0] = ans[0][w-1] ="."
    for j in range(2, w-4, 4):
      ans[0][j] = ans[0][j+1] = ans[0][j+2] = "."
    for j in range(0, w, 2):
      ans[1][j] = "."
    for j in range(0, w+1, 4):
      ans[2][j] = ans[2][j+1] = ans[2][j+2] = "."
    x -= (h-3)+(2*(w//2+1)-2)*2
  else:
    ans[0] = ["."]*w
    ans[1][w-1] = "."
    ans[2] = ["."]*w
    x -= (h-1)+(w-1)

  for i in range(4, h, 2):
    ans[i] = ["."]*w
  for i in range(3, h, 4):
    ans[i][w-1] = "."

  for i in range(5, h, 4):
    y = min(x//2, w-1)
    ans[i][(w-1)-y] = "."
    x -= y*2
  return ans


h, w, x = map(int, input().split())
if h%4 == 3:
  if w%4 == 3:
    ans = solve2(h, w, x)
    for i in ans:
      print("".join(i))
  else:
    ans = solve1(w, h, x)
    if len(ans) == 1:
      print(-1)
    else:
      for i in range(h):
        print("".join([ans[j][i] for j in range(w)]))
else:
  ans = solve1(h, w, x)
  for i in ans:
    print("".join(i))