我自己做这题时想到的是另外的解法（我是边双缩点加换根dp qwq)，并非题解的直接找桥，自己调了一会，最后确实过了。在此留下一个小数据生成器方便对拍。

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <cmath>
#include <cctype>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <numeric>
#include <functional>
#include <climits>
#include <assert.h>
#include <array>
#include <ctime>
#include <cstring>
#include <random>
#include <bitset>
#include <chrono>

#define ll long long
#define ff first
#define ss second
#define please return
#define AC 0
#define YES "YES"
#define NO "NO"
#define Yes "Yes"
#define No "No"
#define endl "\n"
#define sendl " \n"
#define space " "

std::mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());

void solve() {
    int n = rng() % 20;
    int m = n + rng() % 10;
    m = std::min(n * (n - 1), m);
    int k = rng() % n + 1;
    int l = rng() % n + 1;
    std::cout << n << space << m << space << k << space << l << endl;
    std::set<int> se;
    for(int i = 1; i <= k; i++){
        int now = rng() % n + 1;
        while(se.count(now)){
            now = rng() % n + 1;
        }
        se.insert(now);
        std::cout << now << sendl[i == k];
    }
    se.clear();
    for(int i = 1; i <= l; i++){
        int now = rng() % n + 1;
        while(se.count(now)){
            now = rng() % n + 1;
        }
        se.insert(now);
        std::cout << now << sendl[i == l];
    }
    std::set<std::pair<int, int>> se2;
    for(int i = 2; i <= n; i++){
        int x = rng() % i;
        if(x == 0)
            x = 1;
        se2.insert({x, i});
        std::cout << x << space << i << endl;
    }
    m -= n - 1;
    for(int i = 1; i <= m; i++){
        int x = rng() % n + 1;
        int y = rng() % x;
        if(y == 0)
            y = 1;
        
        while(se2.count({y, x}) || x == 1){
            x = rng() % n + 1;
            if(x == 1)
                continue;
            y = rng() % x;
            if(y == 0)
                y = 1;
        }
        se2.insert({y, x});
        std::cout << y << space << x << endl;
    }
}

int main() {
    int t = 1;
	//scanf("%d",&t);
	while(t--) solve();
	return 0;
}