distribute	reads
0-500	269
500-800	126
800-1000	79
1000-1200	95
1200-1400	102
1400-1600	151
1600-1800	255
1800-2000	296
2000-2200	449
2200-2400	580
2400-2600	914
2600-2800	1162
2800-3000	1455
>3000	28689
