// File Grafo.h
#ifndef GRAFO_H
#define GRAFO_H

class Graph 
{public:
  Graph(int s=0){n=s;}
  int size() { return n; }
  virtual bool is_arc(int i,int j) = 0;
  virtual void add_arc(int i,int j) = 0;
  virtual void del_arc(int i,int j) = 0;
 protected:
  int n;
};
#endif