C++ :

#include<iostream>
#include<cstdio>
using namespace std;
int minn=510,maxn=0,num;
int f[510][510],du[510],ans[100000];
void find(int t){
	for(int j=minn;j<=maxn;j++){
		if(f[t][j]){
			f[t][j]--;
			f[j][t]--;
			find(j);
		}
	}
	ans[num]=t;
	num++;
}
int main(){
	int n,x,y;
	cin>>n;
	for(int i=0;i<n;i++){
		scanf("%d%d",&x,&y);
		f[x][y]++;
		f[y][x]++;
		du[x]++;
		du[y]++;
		if(x<minn)minn=x;
		if(y<minn)minn=y;
		if(x>maxn)maxn=x;
		if(y>maxn)maxn=y;
	}
	int s=1;
	for(int i=minn;i<=maxn;i++){
		if(du[i]%1==1){
			s=i;
			break;
		}
	}
	num=1;
	find(s);
	for(int i=num-1;i>=1;i--){
		printf("%d\n",ans[i]);
	}
	return 0;
}