distribute	reads
0-500	670128
500-800	551652
800-1000	244458
1000-1200	188096
1200-1400	149409
1400-1600	121621
1600-1800	99492
1800-2000	81972
2000-2200	69017
2200-2400	57194
2400-2600	47886
2600-2800	40082
2800-3000	34197
>3000	200373
