distribute	reads
0-500	137885
500-800	250543
800-1000	149223
1000-1200	126839
1200-1400	107391
1400-1600	91892
1600-1800	80229
1800-2000	70818
2000-2200	63475
2200-2400	57413
2400-2600	52277
2600-2800	49139
2800-3000	46705
>3000	1168596
