12345678910111213141516171819202122232425272829303132 3334351,2,3456789101112131415161718192021222324252627123?4?567891?2345?678910111213141516?17181920212223?24251234567?891011121314?a?b?a?b?90?a ?b ? a?b?a ?b x? a?b? a ?b ?123452367891011121314151617181920?21222324251. 2. 3. 4. 5. 6. 7.