I have a dataframe like this:

```
           2017      2018      2012  2015  2014  2016
11647  0.044795  0.000000  0.000000   0.0   0.0   0.0
16389  0.089801  0.044900  0.000000   0.0   0.0   0.0
16404  0.014323  0.000000  0.000000   0.0   0.04   0.0
16407  0.052479  0.010442  0.009277   0.0   0.0   0.0
16409  0.000000  0.000000  0.004883   0.0   0.0   5.0

```

Note that columns are not sorted.
For each row, I need to get the latest year with non-zero value.
So the expected result is:

```
11647    2017
16389    2018
16404    2017
16407    2018
16409    2016

```

How to do that?