I am trying to control for province-year fixed effect, but some areas belong to 2 provinces (they are literally on the border of two provinces).
In addition to the largest province, I would like to control for the second-largest province as well, so I tried this code below.

Code:
reg y x i.provincecode1*i.year i.provincecod2*i.year
Then, it drops a lot of samples because many of them just belong to only one province. And, I do not want to lose any samples in the analysis.
What is the most typical way to control for the second-largest province in this case?

FYI, the example of dataset through dataex only produce the sample without the second provinces, so they are missing, but in the actual dataset, some of the areas have province code in provincecode2.

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input int areaid float year double x float y byte(provincecode1 provincecode2)
 7 2005                 0 0 13 .
 7 2006                 0 0 13 .
 7 2007                 0 0 13 .
 7 2008                 0 0 13 .
 7 2009                 0 0 13 .
 7 2010                 0 0 13 .
 7 2011                 0 0 13 .
 7 2012 42474.99346134226 0 13 .
 7 2013                 0 0 13 .
 7 2014                 0 0 13 .
 7 2015                 0 0 13 .
 7 2016                 0 0 13 .
 7 2017                 0 0 13 .
 7 2018                 0 0 13 .
 7 2019                 0 0 13 .
 8 2005                 0 0 17 .
 8 2006                 0 0 17 .
 8 2007                 0 0 17 .
 8 2008                 0 0 17 .
 8 2009                 0 0 17 .
 8 2010                 0 0 17 .
 8 2011                 0 0 17 .
 8 2012                 0 0 17 .
 8 2013                 0 0 17 .
 8 2014 70381.15398588876 0 17 .
 8 2015                 0 0 17 .
 8 2016                 0 0 17 .
 8 2017                 0 0 17 .
 8 2018                 0 0 17 .
 8 2019                 0 0 17 .
19 2005           24497.5 0 13 .
19 2006                 0 0 13 .
19 2007                 0 0 13 .
19 2008                 0 0 13 .
19 2009                 0 0 13 .
19 2010 19913.48828519568 0 13 .
19 2011                 0 0 13 .
19 2012                 0 0 13 .
19 2013                 0 0 13 .
19 2014 39787.19100102393 0 13 .
19 2015                 0 0 13 .
19 2016 15320.73133502453 0 13 .
19 2017                 0 0 13 .
19 2018                 0 0 13 .
19 2019                 0 0 13 .
20 2005                 0 0 13 .
20 2006                 0 0 13 .
20 2007                 0 1 13 .
20 2008             14921 0 13 .
20 2009                 0 0 13 .
20 2010                 0 0 13 .
20 2011                 0 0 13 .
20 2012                 0 0 13 .
20 2013                 0 0 13 .
20 2014                 0 0 13 .
20 2015                 0 0 13 .
20 2016 63502.95938159106 0 13 .
20 2017                 0 0 13 .
20 2018                 0 0 13 .
20 2019                 0 0 13 .
21 2005                 0 0 13 .
21 2006                 0 0 13 .
21 2007                 0 0 13 .
21 2008                 0 0 13 .
21 2009                 0 0 13 .
21 2010                 0 0 13 .
21 2011                 0 0 13 .
21 2012                 0 0 13 .
21 2013                 0 0 13 .
21 2014                 0 0 13 .
21 2015                 0 0 13 .
21 2016 95952.70441376019 0 13 .
21 2017                 0 0 13 .
21 2018 136942.4792154413 0 13 .
21 2019                 0 0 13 .
22 2005                 0 0 13 .
22 2006                 0 0 13 .
22 2007                 0 0 13 .
22 2008                 0 0 13 .
22 2009                 0 0 13 .
22 2010                 0 0 13 .
22 2011                 0 0 13 .
22 2012                 0 0 13 .
22 2013                 0 0 13 .
22 2014                 0 1 13 .
22 2015 91099.37099817435 0 13 .
22 2016                 0 0 13 .
22 2017                 0 0 13 .
22 2018                 0 0 13 .
22 2019                 0 0 13 .
23 2005           30623.5 1 13 .
23 2006 28951.25824817857 0 13 .
23 2007             61746 1 13 .
23 2008 190057.5224913603 0 13 .
23 2009 251975.5429499545 0 13 .
23 2010 263805.3352490551 0 13 .
23 2011  85332.5204794158 0 13 .
23 2012 243574.7360262914 0 13 .
23 2013 1004780.718172329 1 13 .
23 2014 982900.9968104729 0 13 .
end
------------------ copy up to and including the previous line ------------------