while True:
    l=input().split()
    a=int(l[0])
    b=int(l[1])
    if a==0 and b==0:
        break
    else:
        if a%2==0:
            c=a/2
            if b%2==0:
                d=b/2
                while c>0:
                    print(d*"#.")
                    print(d*".#")
                    c=c-2
            else:
                e=b-1
                f=e/2
                while c>0:
                    print(f*"#."+"#")
                    print(f*".#"+".")
                    c=c-2
        else:
            g=a-1
            c=g/2
            if b%2==0:
                h=b/2
                while c>0:
                    print(h*"#.")
                    print(h*".#")
                    c=c-2
                print(h*"#.")
            else:
                i=b-1
                j=i/2
                while c>0:
                    print(j*"#."+"#")
                    print(j*".#"+".")
                    c=c-2
                print(j*"#."+"#")
    print("")
