///findStone(x,y)

found = false

while found = false
{
    inst = instance_find(oStoneBlock,irandom(instance_number(oStoneBlock)-1))
    var path = path_add()
    found = mp_grid_path(global.aigrid,path,argument0,argument1,inst.x,inst.y,true)
    path_delete(path)
}
return inst