1: Throw two grenades there. One to remove the stone and one to fall and remove the first stone under the plank. 2. Throw two grenades there. One to remove the stone and one to fall and remove the second stone under the plank. 3. Throw one grenade into the white box. That will explode the big stone. 4. Throw one grenade there so that it lands on the third stone. 5. Once the plank has fallen, throw the last grenade to bomb the enemy.