import sys
write=sys.stdout.write

h_numbers=[]
w_numbers=[]

while True:
    numbers=[]
    numbers=input().split()
    numbers[0]=int(numbers[0])
    numbers[1]=int(numbers[1])
    if numbers[0]==0 and numbers[1]==0:
        break
    h_numbers.append(numbers[0])
    w_numbers.append(numbers[1])

for i in range(0,len(h_numbers)):
    for j in range(0,h_numbers[i]):
        for k in range(0,w_numbers[i]):
            if (j+k+2)%2==0:
                write('#')
            else:
                write('.')
        print()