#include<iostream>
#include<vector>
#include<map>
using namespace std;
int getindex(vector<int> &moka, int v){
	for(int i=0;i<moka.size();i++)
		if(moka[i] == v)
			return i;
	return -1;
}
int main(){
	int n =0;
	cin>>n;
	map<int, int> stds;
	map<int, int>::iterator it;
	vector<int> moka(n);
	for(int i=0;i<n;i++){
		moka[i] = -1;
	}
	int f, b;
	int f1, b1;
	int fn, bn;
	for(int i=0;i<n;i++){
		cin>>f>>b;
		if(f ==0 )
		{
			f1 = f;
			b1 = b;
		}
		if(b == 0)
		{
			fn = f;
			bn = b;
		}
		stds.insert(make_pair(f,b));
	}
	moka[1] = b1;
	moka[n-2] = fn;
	for(it = stds.begin();it!=stds.end();it++){
		if(it->first != 0 && it->second != 0){
			f = it->first;
			b = it->second;
			int ixF = getindex(moka,f);
			int ixB = getindex(moka,b);
			if(ixF != -1){
				if(ixF+2<n)
					moka[ixF +2] = b;
			}
			if(ixB != -1){
				if(ixB-2>=0)
					moka[ixB-2] = f;
			}
		}
	}
	for(int i=0;i<moka.size();i++){
		cout<<moka[i]<<" ";
	}
	cout<<endl;
	return 0;
}