Start by converting to polar coordinates:
Now we can see that the solutions are n=...-12,-8,-4,0,4,8,12 ...
n=-4000 is an integer less than 0 and so -4000 is also a solution. There is no unique smallest solution because for any solution n, n-4 is also a solution.
If your question actually asked for the "smallest positive integer" then the answer would be 4.