0 1 2 3 4 5 6 7 8 9 
len: 10

0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 len: 20

0 1 2 3 4 5 6 7 8 9 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 len: 30

0 1 2 3 4 5 6 7 8 9 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 5 6 7 8 9 len: 40