import sys 
line = sys.stdin.readline() 
while line : 
 H,W = map(int,line.split()) 
 if H == 0 and W == 0: break;
  for i in range(0,H):
   for j in range(0,W):
    if (i+j)%2 == 0: sys.stdout.write("#") 
    else: sys.stdout.write(".") 
          print ""
	print ""
 line = sys.stdin.readline()
