public void store(Out out){
        out.println(this.V);
        out.println(this.size);
        
        // |V| lines of lin labels
        for(int v = 0; v < this.V; v++){
            for(int n : this.labels[v].lin){
                out.print(n + " ");
            }
            out.println();
        }
        
        
        // |V| lines of lout labels
        for(int v = 0; v < this.V; v++){
            for(int n : this.labels[v].lout){
                out.print(n + " ");
            }
            out.println();
        }
        
        out.close();
    }