distribute	reads
0-500	1450632
500-800	850140
800-1000	285564
1000-1200	173926
1200-1400	116407
1400-1600	83141
1600-1800	64104
1800-2000	51314
2000-2200	42399
2200-2400	36091
2400-2600	31400
2600-2800	27567
2800-3000	24901
>3000	509872
