distribute	reads
0-500	3565470
500-800	1584029
800-1000	718357
1000-1200	554180
1200-1400	441236
1400-1600	361784
1600-1800	302585
1800-2000	259033
2000-2200	221673
2200-2400	193713
2400-2600	169673
2600-2800	150714
2800-3000	134292
>3000	1566644
