Update 22nd Oct, 2011: Cache was relocated about 30 meters towards Northwest and calculations edited accordingly.
This place is actually worth seeing only in Spring when migratory birds return to Finland. In Summer the place turns into a jungle, in Autumn it's rather sad sight and in Winter the box is probably under snow. So don't get disappointed if you go there.
At given coordinates you'll find a sign with a number on it. Let that number be A.
There's a vertical construction nearby. It has three levels. Let the number of steps from ground to first level be B (1st level included).
On the top-level there's small 'alcove' with three 'walls'. Let the number of vertical planks on its shortest wall be C.
where xxx=(4*A*C)+A+C+15 and yyy=(25*B)-C-14
Cache cannot be found when there's snow on ground.