while True:
    input=input().split()
    H=int(input[0])
    W=int(input[1])
    if H==0:
        break
    for i in range(1,H+1):
        if i%2!=0:
            if W%2==0:
                print("#."*(W/2))
            if W%2!=0:
                print("#."*(W/2)+".")
        if i%2==0:
            if W%2==0:
                print(".#"*(W/2))
            if W%2!=0:
                print(".#"*(W/2)+".")
    print()
