/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
#include <stdio.h>
#include <stdlib.h>
main()
  { int i, j, adj[V][V];
    for (i = 0; i < V; i++)
      for (j = 0; j < V; j++) 
        adj[i][j] = 0;
    for (i = 0; i < V; i++) adj[i][i] = 1;
    while (scanf("%d %d\n", &i, &j) == 2)
      { adj[i][j] = 1; adj[j][i] = 1; }
  }