#include <bits/stdc++.h>
using namespace std;
const int N =1e3;

int main(){
	int n,m;
	cin>>n>>m;
	vector<vector<int>> a(N, vector<int>(0));
	while(m--){
		int x,y;
		cin>>x>>y;
		a[x-1].push_back(y);//也是从0开始的
	}
	for(int i = 0 ; i < n ; i++){
		sort(a[i].begin(),a[i].end());
	}
	for(int i = 0 ; i < n ; i++){
    	cout<<a[i].size()<<" ";
        for(int j = 0 ; j < a[i].size(); j++){
            cout<<a[i][j]<<" ";
        }
        cout<<endl;
    }
    return 0;
}