count = 0
while 1:
    if(count != 0):
        print()
    count += 1
    H, W = map(int, input().split())
    if(H == 0 and W == 0):
        break
    for i in range(H):
        if(i != 0):
            print()
        for j in range(W):
            if(i%2 == 0):
                if(j%2 == 0):
                    print('#',end="")
                else:
                    print('.',end="")
            else:
                if(j%2 == 0):
                    print('.',end="")
                else:
                    print('#',end="")

