distribute	reads
0-500	63843
500-800	204048
800-1000	149082
1000-1200	113165
1200-1400	78471
1400-1600	53699
1600-1800	37424
1800-2000	26042
2000-2200	18382
2200-2400	13053
2400-2600	9347
2600-2800	6698
2800-3000	4960
>3000	15481
