distribute	reads
0-500	643320
500-800	332233
800-1000	144981
1000-1200	112811
1200-1400	91054
1400-1600	79173
1600-1800	67487
1800-2000	57730
2000-2200	50994
2200-2400	45845
2400-2600	41865
2600-2800	39634
2800-3000	36656
>3000	621268
