func_code_string: #include <bits/stdc++.h>   const long long N = 500005;   const long long mod = 1e9 + 7;   using namespace std;   std::vector<long long> adj[N];   std::vector<bool> vis(N);   void solve() {     long long n, m, k, x = 0, y = 0, c = 0, q, ans = 0;     cin >> n >> m;     for (long long i = 0; i < m; ++i) {       cin >> x >> y;       adj[x].push_back(y);       adj[y].push_back(x);     }     x = 0;     for (int i = 1; i <= n; ++i) {       if (x < adj[i].size()) {         x = adj[i].size();         y = i;       }     }     std::vector<pair<long long, long long> > v;     queue<long long> nodes;     nodes.push(y);     vis[y] = 1;     while (!nodes.empty()) {       x = nodes.front();       nodes.pop();       for (auto i : adj[x]) {         if (!vis[i]) {           vis[i] = 1;           nodes.push(i);           v.push_back({x, i});         }       }     }     for (int i = 0; i < v.size(); ++i) {       cout << v[i].first <<     << v[i].second <<   n ;     }   }   signed main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     long long T = 1;     while (T--) {       solve();     }     return 0;   }   