/*
  This code is from "Algorithms in C, Third Edition,"
  by Robert Sedgewick, Addison Wesley Longman, 1998.
*/

/* prog1.2.c */
#include <stdio.h>
#define N 10000
int main()
{
  int i, j, p, q, id[N];
  for (i = 0; i < N; i++)
    id[i] = i;
  while (scanf("%d %d\n", &p, &q) == 2) {
    for (i = p; i != id[i]; i = id[i]);
    for (j = q; j != id[j]; j = id[j]);
    if (i == j)
      continue;
    id[i] = j;
    printf(" %d %d\n", p, q);
  }
  return 0;
}