distribute	reads
0-500	1312262
500-800	822625
800-1000	280075
1000-1200	176505
1200-1400	116219
1400-1600	80438
1600-1800	58050
1800-2000	42490
2000-2200	32758
2200-2400	25347
2400-2600	19882
2600-2800	15981
2800-3000	13127
>3000	85901
