#include<bits/stdc++.h>
using namespace std;
 
int main()
{
    int node, edge;
    cin>>node>>edge;
    vector<int>graph[node+1];
 
    int u, v;
    for(int i = 1; i <= edge; i++)
    {
        cin>>u>>v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }
 
    for(int i = 1; i <= node; i++)
    {
        cout<<i<<" -> ";
        for(int j = 0; j < graph[i].size(); j++)
        {
            cout<<graph[i][j]<<" ";
        }
        cout<<endl;
    }
 
}
 

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1 2
2 3
3 4
4 1
2 4