distribute	reads
0-500	1895965
500-800	695006
800-1000	274778
1000-1200	200872
1200-1400	154201
1400-1600	122471
1600-1800	101174
1800-2000	85437
2000-2200	72411
2200-2400	61892
2400-2600	54907
2600-2800	48242
2800-3000	42987
>3000	711996
