lambda 5/4 # sourlas part: 1x1 I 1/2 at 3/4,1/2 1x2 P 1/4 at 0/1,1/2 1x2 P 1/4 at 0/1,1/2 1x2 P 1/4 at 0/1,1/2 # stair part 2x1 P 1/2 at 1/4,0/1 1x2 P 1/4 at 0/1,0/1 2x1 P 1/8 at 0/1,3/8 # puncturing 1 p 1/4 at 0/1