distribute	reads
0-500	1019251
500-800	465364
800-1000	187957
1000-1200	140143
1200-1400	109956
1400-1600	91051
1600-1800	77957
1800-2000	68283
2000-2200	60823
2200-2400	54891
2400-2600	50505
2600-2800	46595
2800-3000	43556
>3000	1105887
