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