#include <cstdio>
#include <stack>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <functional>
#include <cstring>
#include <algorithm>
#include <cctype>
#include <string>
#include <map>
#include <iomanip>
#include <cmath>
#define LL long long
#define ULL unsigned long long
#define SZ(x) (int)x.size()
#define Lowbit(x) ((x) & (-x))
#define MP(a, b) make_pair(a, b)
#define MS(arr, num) memset(arr, num, sizeof(arr))
#define PB push_back
#define F first
#define S second
#define ROP freopen("input.txt", "r", stdin);
#define MID(a, b) (a + ((b - a) >> 1))
#define LC rt << 1, l, mid
#define RC rt << 1|1, mid + 1, r
#define LRT rt << 1
#define RRT rt << 1|1
#define BitCount(x) __builtin_popcount(x)
#define BitCountll(x) __builtin_popcountll(x)
#define LeftPos(x) 32 - __builtin_clz(x) - 1
#define LeftPosll(x) 64 - __builtin_clzll(x) - 1
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
using namespace std;
const double eps = 1e-6;
const int MAXN = 2e5 + 10;
const int MOD = 1000007;
typedef pair<int, int> pii;
typedef vector<int>::iterator viti;
typedef vector<pii>::iterator vitii;
  
struct POINT
{
    int pre, next;
    bool operator < (const POINT &a) const
    {
        return pre < a.pre;
    }
}pit[MAXN];
  
int ans[MAXN], in[MAXN], out[MAXN], n;
map<int, int> inMap, outMap;
  
int Solve(int val)
{
    int l = 0, r = n, mid;
    while (l < r)
    {
        mid = MID(l, r);
        if (pit[mid].pre == val) return mid;
        if (pit[mid].pre < val) l = mid + 1;
        else r = mid;
    }
    return -1;
}
  
  
int main()
{
    //ROP;
    int i, j;
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
    {
        int a, b;
        scanf("%d%d", &pit[i].pre, &pit[i].next);
        inMap[pit[i].pre]++, outMap[pit[i].next]++;
    }
    sort(pit, pit + n);
    int pos = 2;
    int curPeo = pit[0].next;
    while (curPeo != 0)
    {
        ans[pos] = curPeo;
        pos += 2;
        int tmpPos = Solve(curPeo);
        if (tmpPos == -1) break;
        curPeo = pit[tmpPos].next;
    }
    pos = 1;
    for (i = 1; i <= n; i++)
    {
        if (inMap[pit[i].pre] == 1 && outMap[pit[i].pre] == 0)
        {
            curPeo = pit[i].pre;
            break;
        }
    }
    ans[pos] = curPeo; curPeo = pit[i].next;
    pos += 2;
    while (curPeo != 0)
    {
        ans[pos] = curPeo;
        pos += 2;
        int tmpPos = Solve(curPeo);
        if (tmpPos == -1) break;
        curPeo = pit[tmpPos].next;
    }
    for (i = 1; i <= n; i++) printf("%d ", ans[i]);
    return 0;
}