private static void net2g(){
        File[] net = Data.getFiles(Data.DATA_ORIGIN, ".net");
        
        for(File f : net){
            String g = f.getAbsolutePath() + ".g";
            StdOut.println(f.getName() + "\tnet -> <v, w>\t" + g);
            
            In in = new In(f);
            Out out = new Out(g);
            
            out.println(in.readLine()); // for V
            out.println(in.readLine()); // for E
            
            while(in.hasNextLine()){
                String[] nums = in.readLine().split(" ");
                for(int i = 1; i < nums.length; i++){
                    out.println(nums[0] + " " + nums[i]);
                }
            }
            
            in.close();
            out.close();
        }
    }