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

/* prog1.1.c */
#include <stdio.h>
#define N 10000
int main()
{
  int i, p, q, t, id[N];
  for (i = 0; i < N; i++)
    id[i] = i;
  while (scanf("%d %d\n", &p, &q) == 2) {
    if (id[p] == id[q])
      continue;
    for (t = id[p], i = 0; i < N; i++)
      if (id[i] == t)
	id[i] = id[q];
    printf(" %d %d\n", p, q);
  }
  return 0;
}