... duong2chieu (12 , 18 ) = 1 duong2chieu (18 , 12 ) = 1 duong2chieu (18 , 19 ) = 1 duong2chieu (19 , 24) = 1 duong2chieu (10 , 11 ) = 1 duong2chieu (11 , 10 ) = 1 duong2chieu (10 , 9) = 1 duong2chieu(7, 13 ) = 1 duong2chieu (13 , ... duong2chieu (13 , 7) = 1 duong2chieu(8, 14 ) = 1 duong2chieu (14 , 8) = 1 duong2chieu (13 , 14 ) = 1 duong2chieu (14 , 15 ) = 1 duong2chieu (14 , 21) = 1 duong2chieu( 21, 14 ) = 1 duong2chieu (13 , 25) = 1 duong2chieu(25, ... 1 duong2chieu(6, 5) = 1 duong2chieu(5, 9) = 1 duong2chieu(9, 5) = 1 duong2chieu(9, 8) = 1 duong2chieu(6, 11 ) = 1 duong2chieu (11 , 6) = 1 duong2chieu (12 , 11 ) = 1 duong2chieu (11 , 12 ) = 1 ...