#include <bits/stdc++.h>

using namespace std;
ifstream f(".in");
ofstream g(".out");
int a[3][100001],n,st[100001];
void citire()
{
    f>>n;
    int x,y,k=0;
    while(f>>x>>y)
    {
        k++;
        a[1][k]=y;
        a[2][k]=st[x];
        st[x]=k;

    }
}
void afis(int x)
{
        g<<x<<" ";
        int unde=st[x];
        while(unde!=0)
        {
            g<<a[1][unde]<<" ";
            unde=a[2][unde];
        }
        g<<endl;
}
int main()
{     int i;
     citire();
     for(i=1; i<=n; i++)
             afis(i);


    return 0;
}