while True:

    H, W =(int(i) for i in input().split())
    line1, line2 = "", ""
    line3, line4 ="#", "."
    if H == 0 and W ==0:
        break
    
    elif W % 2 == 0:
        for i in range(W//2):
            line1 += "#."
            line2 += ".#"
        if H % 2 == 0:
            for i in range(H//2):
                print(line1, "\n", line2, "\n")
        else:
            print(line1)
            for i in range(H//2):
                print(line2)
                print(line1)
            print()
            
    
    
    else:
        for i in range(W//2):
            line3 += ".#"
            line4 += "#."
        if H % 2 == 0:
            for i in range(H//2):
                print (line3)
                print (line4)
            print()
        else:
            print(line3)
            for i in range(H//2):
                print(line4)
                print(line3)
            print()
    
    