private boolean getFreeCell(ERow row){
        int i =0;
        for (i = 0; i < size; i++) {
            if(U[row.getXs()[i]][row.getYs()[i]] == 0)
                break;
        }
        if(i<size){
            x = row.getXs()[i];
            y = row.getYs()[i];
            System.out.println("free " + x + ":" + y);
            return true;
        }
        else
        {
            return false;
        }
    }