import sys
 
while True:
    h, w = [ int( val ) for val in sys.stdin.readline().split( " " ) ]
    if 0 ==h and 0 == w:
        break
    pa = [ "#", "." ]
    d = 0
    ouput = []
    for i in range( h ):
        d = i&1
        for j in range( w ):
            ouput.append( pa[d] )
            d = not d   
        ouput.append( "\n" )    
    print( "".join( ouput ) )