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

using ll = long long;

// 制約に書かれている定数を宣言
const ll Nmin = 1, Nmax = 200000;
const ll Mmin = 1, Mmax = 200000;

int main(){
    registerValidation();
    ll N = inf.readLong(Nmin, Nmax);
    inf.readSpace();
    ll M = inf.readLong(Nmin, Nmax);
    inf.readEoln();
    assert(M <= N * N);
    vector<pair<int, int>> E(M);
    for(int i = 0; i < M; i++){
        ll u = inf.readLong(1, N);
        inf.readSpace();
        ll v = inf.readLong(1, N);
        inf.readEoln();
        E[i] = pair<int,int>{u, v};
    }
    sort(E.begin(), E.end());
    for(int i = 0; i < M-1; i++){
        assert(E[i] != E[i+1]);
    }
    inf.readEof();
}