#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n, m, x, y;
    cin >> n >> m;
    map<int, vector<int>> arr;

    for (int i = 0; i < m; i++)
    {
        cin >> x >> y;
        arr[x].push_back(y);
    }

    for (auto &ele : arr)
    {
        sort(ele.second.begin(), ele.second.end());
    }
    
    for (int i = 1; i <= n; i++)
    {
        cout << arr[i].size();
        for (auto &num : arr[i])
        {
            cout << " " << num;
        }
        cout << endl;
    }
    
    return 0;
}