while True:
    H,W = map(int,input().split())
    if H==W==0:
        break
    num = H * W
    for i in range(0,num):
        if i % 2 == 0:
            for j in range(0,W):
                if j % 2 == 0:
                    print("#")
                if j % 2 == 1:
                    print(".")
        if i % 2 == 1:
            for j in range(0,W):
                if j % 2 == 0:
                    print(".")
                if j % 2 == 1:
                    print("#")
    print()
