4
0 0 U D U U 
0 1 D D U U 
0 2 U D D U 
0 3 U D U U 
1 0 U D U D 
1 1 U D U D 
1 2 U D U D 
1 3 U D U D 
2 0 U D U D 
2 1 U D U D 
2 2 U D U D 
2 3 U D U D 
3 0 D U U D 
3 1 U U D D 
3 2 D U U D 
3 3 U U D D