#include<bits/stdc++.h>
using namespace std;
int const ext=1000004;
int n, a, b, visits, out[ext];
vector<int> graph[ext], cycle;
bool visited[ext], debug=1;


void find_cycle(int v, int u){
    int w=u;
    cycle.push_back(w);
    while(w!=v && w!=0){
        w=out[w];
        cycle.push_back(w);
    }
    if(cycle[cycle.size()-1]==0)
        cycle.pop_back();
    return;
}


void dfs(int v){
    visited[v]=true;
    visits++;
    for(int i=0; i<graph[v].size(); i++){
        if(visited[graph[v][i]] && out[graph[v][i]]!=v)
            find_cycle(v, graph[v][i]);
        if(!visited[graph[v][i]]){
            dfs(graph[v][i]);
            out[v]=graph[v][i];
        }
    }
    return;
}

int main(){
    scanf("%d", &n);
    for(int i=1; i<n+1; i++){
        scanf("%d%d", &a, &b);
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    a=1;
    while(visits<n){
        while(visited[a])
            a++;
        dfs(a);
        while(cycle.size()>0){
            printf("%d ", cycle[cycle.size()-1]);
            cycle.pop_back();
        }
        printf("\n");
    }
    return 0;
}