没题解

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
const int N = 1e6 + 5;
int n, x, y, T;
int vis[N], match[N];
vector<int> G[N];

bool dfs(int x){
    if (vis[x] == T) return false;
    vis[x] = T;
    for (int to : G[x]){
        if (!match[to] || dfs(match[to])){
            match[to] = x;
            return true;
        }
    }
    return false;
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    cin >> n;
    for (int i=1; i<=n; i++){
        cin >> x >> y;
        G[x].push_back(i);
        G[y].push_back(i);
    }
    for (T=1; T<=10005; T++){
        if (!dfs(T)){
            cout << T - 1 << endl;
            return 0;
        }
    }
    return 0;
}