distribute	reads
0-500	0
500-800	1
800-1000	2
1000-1200	8
1200-1400	7
1400-1600	12
1600-1800	17
1800-2000	31
2000-2200	54
2200-2400	61
2400-2600	117
2600-2800	169
2800-3000	232
>3000	1951
