df has an integer column 'X'. For each value, count the distance back to the previous zero (or the start, whichever is closer). Return this as a Series.

Input

   X
0  7
1  2
2  0
3  3
4  4
5  2
6  5
7  0
8  3
9  4

Output

0    1
1    2
2    0
3    1
4    2
5    3
6    4
7    0
8    1
9    2
Name: Y, dtype: int64