记录

$code$

#include <bits/stdc++.h>
using namespace std;
#define hh putchar('\n')
#define kg putchar(' ')
#define debug puts("debug")
//#define int long long
//#define int __int128
namespace quickread{
	inline int read(){
		int x=0,f=1;char ch=getchar();
		while (ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
		while (ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
		return x*f;
	}
	inline void write(int x){
	    if(x<0){putchar('-');x=-x;}
	    if(x>9)write(x/10);
	    putchar(x%10+'0');
	}
	inline string readstr(){
    	char ch=getchar();string str="";
		while(!(ch>='0'&&ch<='9')&&!(ch>='a'&&ch<='z')&&!(ch>='A'&&ch<='Z')) ch=getchar();
		while((ch>='0'&&ch<='9')||(ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z')){str+=ch;ch=getchar();}
		return str;
	}
	inline char readchar(){
		char ch=getchar();
		while(!(ch>='0'&&ch<='9')&&!(ch>='a'&&ch<='z')&&!(ch>='A'&&ch<='Z')) ch=getchar();
		return ch;
	}
}
using namespace quickread;
int n,m,bg,top,st[100010];
vector<int> p[510];
vector<int>::iterator it[100010];
bool vis[510][510];
void hierholzers(){
	for(int i=1;i<=n;i++){
		int d=p[i].size();
		if(d%2==1) {bg=i;break;}
	}
	for(int i=1;i<=n;i++){
		sort(p[i].begin(),p[i].end());
		it[i]=p[i].begin();
	}
	if(!bg){
		bg=510;
		for(int i=1;i<=n;i++)
			if(p[i].size()&&bg>i) bg=i; 
	}
}
void dfs(int u){
	while(it[u]!=p[u].end()){
		int v=*it[u];it[u]++;
		if(vis[u][v]) continue;
		vis[u][v]=vis[v][u]=1;
		dfs(v);
	}
	st[++top]=u;
}
signed main(){
//	ios::sync_with_stdio(0);
//	cin.tie(0);cout.tie(0);
	m=read();
	for(int i=1;i<=m;i++){
		int u=read(),v=read();
		p[u].push_back(v);
		p[v].push_back(u);
		n=max(n,max(u,v));
	}
	hierholzers();
	dfs(bg);
	for(int i=top;i>=1;i--) write(st[i]),hh;;
	return 0;
}