Pekeris waveguide. 
N I  J
20 0
3
0 0 0 0 0 0 0
0 1500 0 0 0 1 0
100 1800 0 0 0 1.8 0 
95
99 99 1 1
150 1E8
2048 1 1000
0 3 20 0.5
20 80 12 10
0 100 12 20
40 70 6