while 1 do
a,b=gets.split.map(&:to_i)
if a!=0 || b!=0 then
for i1 in 1..a do
if i1%2==1 then
for i2 in 1..b do
if i2%2==0 then
print "."
else
print "#"
end
end
else
for i2 in 1..b do
if i2%2==0 then
print "#"
else
print "."
end
end
end
print "\n"
end
else break
end
print "\n"
end