def main():
    h, w, k = list(map(int, input().split()))
    if k == 0:
        for y in range(h):
            print("."*w)
        return 
    if h == 1:
        if k == 1:
            print("#"+"."*(w-1))
        else:
            print(-1)
        return
    if w == 1:
        if k == 1:
            print("#")
            for y in range(h-1): print(".")
        else:
            print(-1)
        return
    if k == 1:
        print(-1)
        return
    if h == 2:
        if 2 <= k <= w:
            print("#"*(k-1)+"."*(w-k+1))
            print("."*w)
        else:
            print(-1)
        return
    if w == 2:
        if 2 <= k <= h:
            for _ in range(k-1):
                print("#.")
            for _ in range(w-k+1):
                print("..")
        else:
            print(-1)
        return
    assert 0

main()