On the right side of Ostradnoye, you can find an abandoned hut. There, you will find a shelter, where you can find some interesting, hidden things.
In the cottage you will find a light switch when you turn it on, a flap will appear on the floor. Then you will be able to move the bed and get to the flap.
Open the flap and go down to the shelter hidden under the cottage.
In the shelter, you will find a desk, two cabinets and a locked safe.
On one shelf you will find a Wooden Assault Rifle.