H = []
W = []
while(True):
    x,y = map(int,input().split())
    if x == 0 and y == 0:
        break
    else:
        H.append(x)
        W.append(y)
for i in range(len(H)):
    for j in range(H[i]):#行数
        if j+1 == H[i] and j%2 == 0:
            print(round(W[i]/2)*"#."+"\n")
        elif j+1 == H[i] and j%2 == 1:
            print(round(W[i]/2)*".#"+"\n")
        elif j%2 == 0:
            print(round(W[i]/2)*"#.")
        else:
            print(round(W[i]/2)*".#")
