#include <bits/stdc++.h>
using namespace std;
int check[1000001] = {0};
pair<int, int> pii[1000000];
int main() {
  map<int, int> m1, m2;
  queue<int> q;
  int n;
  cin >> n;
  int a, b, second, first;
  for (int i = 0; i < n; i++) {
    cin >> a >> b;
    m1[a] = b;
    m2[b] = a;
    pii[i].first = a;
    pii[i].second = b;
    if (a == 0) second = b;
    if (b == 0) first = a;
  }
  check[0] = 1;
  int ans[n + 1];
  for (int i = 2; i <= n; i += 2) {
    ans[i] = second;
    second = m1[second];
    check[ans[i]] = 1;
  }
  int loc;
  for (int i = 0; i < n; i++) {
    if (check[pii[i].first] == 0) {
      loc = pii[i].second;
      break;
    }
  }
  if (n % 2 == 0) loc = first;
  while (m2[loc] != 0) {
    loc = m2[loc];
  }
  while (loc != 0) {
    q.push(loc);
    loc = m1[loc];
  }
  int k = 1;
  while (!q.empty()) {
    ans[k] = q.front();
    k += 2;
    q.pop();
  }
  for (int i = 1; i <= n; i++) {
    cout << ans[i] << " ";
  }
}
