#include <stdio.h>
#include <stdlib.h>

#define Vertex int

struct digraph {
  int V; 
  int A; 
  int *adj; 
};

typedef struct digraph *Digraph;
typedef struct node *link;
    struct node { 
      Vertex w; 
      link next; 
    };

link NEW (Vertex w, link next) { 
  link x = malloc(sizeof *x);
  x->w = w; 
  x->next = next;     
  return x;                         
}

Digraph DIGRAPHinit (int V) {   
  Digraph G = malloc(sizeof *G);
  G->V = V; 
  G->A = 0;
  G->adj = malloc(V * sizeof(link));
  int v;
  for (v = 0; v < V; v++) 
    G->adj[v] = NULL;
  return G;
}

void DIGRAPHinsertA (Digraph G, Vertex v, Vertex w) { 
  link p;
  if (v == w) return;
  for (p = G->adj[v]; p != NULL; p = p->next) 
          if (p->w == w) return;
  G->adj[v] = NEW(w, G->adj[v]);
  G->A++;
}