#(34)フレームの描画
while True:
    H,W = [int(x) for x in input().split()]
    
    if (H,W)==(0,0): 
        break
    
    unit = "#."
    
    for i in range(H):
        print( unit*(W//2) + unit[0]*(W%2) )
        
        unit = unit[1] + unit[0]
    print("")
