N D T: a1
N D T: a2
N D T: a3
N D T: a4
N D T: a5
N D T: a6
N D T: a7
N D T: a8
N D T: b1
N D T: b2
N D T: b3
N D T: b4
N D T: b5
N D T: bb1
N D T: bb2
N D T: bb3
N D T: bb4
N D T: bb5
N D T: aa1
N D T: aa2
N D T: aa3
N D T: aa4
N D T: aa5
N D T: aa6
N D T: aa7
N D T: aa8
N D T: case 2
N D T: case1
N D T: casea1
N D T: casea3