distribute	reads
0-500	10675548
500-800	3795246
800-1000	1255879
1000-1200	834262
1200-1400	596639
1400-1600	448917
1600-1800	352369
1800-2000	284244
2000-2200	234296
2200-2400	198583
2400-2600	169345
2600-2800	147383
2800-3000	129350
>3000	1607963
