#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(),x.end()
const ll MAXN=1e6+5,MOD=998244353,INF=1e9,LG=16,MAX=2e6;
ll i,n,m,j,k,p,t,ans,nex[MAXN],pre[MAXN],b[MAXN];
struct h{
    ll pre,suf;
} a[MAXN];
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    // freopen("changedir.inp","r",stdin);
    // freopen("changedir.out","w",stdout);
    cin>>n;
    for(i=1;i<=n;i++){
        cin>>a[i].pre>>a[i].suf;
        nex[a[i].pre]=a[i].suf;
        pre[a[i].suf]=a[i].pre;
    }
    ll cur=nex[0],id=2;
    while(cur!=0){
        b[id]=cur;
        ll luu=cur;
        cur=nex[cur];
        nex[luu]=0;
        pre[luu]=0;
        id+=2;
    }
    for(i=1;i<=MAX;i++){
        if(nex[i]&&!pre[i]){
            cur=i;
            break;
        }
    }
    id=1;
    while(cur!=0){
        b[id]=cur;
        ll luu=cur;
        cur=nex[cur];
        nex[luu]=0;
        pre[luu]=0;
        id+=2;
    }
    for(i=1;i<=n;i++)
        cout<<b[i]<<" ";
}