distribute	reads
0-500	51
500-800	16
800-1000	13
1000-1200	11
1200-1400	11
1400-1600	8
1600-1800	12
1800-2000	16
2000-2200	12
2200-2400	20
2400-2600	34
2600-2800	22
2800-3000	13
>3000	67
