import math
a=[]
i=0
while 1:
    l=input().split()

    h=int(l[0])
    w=int(l[1])

    if h==0 and w==0:
        break
    else:
        a.append(h)
        a.append(w)
        i=i+2

m=0
n=0
while m<i:
    b=math.floor(a[m+1]/2)
    while n<a[m]:
        if a[m+1]%2==0:
            if n%2==0:
                print("#."*b)
            else:
                print(".#"*b)
        else:
            if n%2==0:
                print("#."*b+"#")
            else:
                print(".#"*b+".")
        n=n+1
    print("")
    m=m+2

