distribute	reads
0-500	587
500-800	195
800-1000	138
1000-1200	102
1200-1400	91
1400-1600	102
1600-1800	77
1800-2000	86
2000-2200	91
2200-2400	78
2400-2600	76
2600-2800	70
2800-3000	56
>3000	4829
