#include <iostream>
#include <cstdio>
#include <vector>
#include <utility>
#include <algorithm>
#include <queue>
using namespace std;

#define pb push_back

vector <int> a[50001];
int n,m,x,y;
int viz[50001];
vector <int> rez;


void topo(int q)
{
    viz[q]=1;
    for(int i=0;i<a[q].size();i++)
        if(viz[a[q][i]]==0)
    {
        rez.pb(a[q][i]);
        topo(a[q][i]);
    }
}

void citire()
{
    scanf("%d%d",&n,&m);
    for(int i=0;i<n;i++)
    {
        scanf("%d%d",&x,&y);
        a[x].pb(y);
    }
    for(int i=0;i<n;i++)
        sort(a[i].begin(),a[i].end());
}

int main()
{
    freopen("sortaret.in","r",stdin);
    freopen("sortaret.out","w",stdout);
    citire();
    rez.pb(1);
    topo(1);
    for(int i=0;i<rez.size();i++)
        printf("%d ",rez[i]);
    return 0;
}