func_code_string: #include <bits/stdc++.h>   using namespace std;   using namespace chrono;   const int infinity = (int)1e9 + 42;   const int64_t llInfinity = (int64_t)1e18 + 256;   const int module = (int)1e9 + 7;   const long double eps = 1e-8;   mt19937_64 randGen(system_clock().now().time_since_epoch().count());   inline void raiseError(string errorCode) {     cerr <<  Error :   << errorCode << endl;     exit(42);   }   signed main() {     ios_base::sync_with_stdio(false);     int n, m;     cin >> n >> m;     vector<vector<int> > g(n);     for (int i = 0; i < m; i++) {       int a, b;       cin >> a >> b;       a--;       b--;       g[a].push_back(b);       g[b].push_back(a);     }     vector<int> d(n, INT_MAX);     vector<int> p(n, -1);     queue<int> q;     q.push(0);     d[0] = 0;     while (!q.empty()) {       int v = q.front();       q.pop();       for (int to : g[v]) {         if (d[to] == INT_MAX) {           d[to] = d[v] + 1;           p[to] = v;           q.push(to);         }       }     }     int ans1 = d[n - 1];     int idx2 = -1;     for (int i = 0; i < n; i++) {       if (d[i] == 2) {         idx2 = i;         break;       }     }     if (ans1 > 4 && idx2 >= 0) {       cout << 4 << endl;       cout << 1 <<     << p[idx2] + 1 <<     << idx2 + 1 <<     << 1 <<     << n            << endl;       return 0;     }     if (ans1 > 5) {       vector<char> used(n, false);       vector<vector<int> > komps;       vector<int> kompId(n, -1);       used[0] = true;       function<void(int)> dfs = [&](int v) {         if (used[v]) {           return;         }         used[v] = true;         kompId[v] = (int)komps.size() - 1;         komps.back().push_back(v);         for (int to : g[v]) {           dfs(to);         }       };       for (int i : g[0]) {         if (!used[i]) {           komps.emplace_back();           dfs(i);         }       }       for (int i = 0; i < n; i++) {         sort(g[i].begin(), g[i].end());       }       for (auto &komp : komps) {         sort(komp.begin(), komp.end());         bool klika = true;         int ngsz = (int)komp.size();         int x = -1, y = -1;         for (int i : komp) {           if ((int)g[i].size() == ngsz) {             continue;           }           for (int j : komp) {             if (i == j) {               continue;             }             if (!binary_search(g[i].begin(), g[i].end(), j)) {               x = i;               y = j;               break;             }           }           if (x < 0 || y < 0) {             for (;;)               ;           }           klika = false;           break;         }         if (klika) {           continue;         }         int z = -1;         vector<int> xReach;         for (int i = 1; i < n; i++) {           if (i == x || i == y) {             continue;           }           bool findX = binary_search(g[i].begin(), g[i].end(), x);           bool findY = binary_search(g[i].begin(), g[i].end(), y);           if (findX && findY) {             z = i;             break;           } else if (findX) {             xReach.push_back(i);           }         }         if (z < 0) {           z = -1;           for (int i : xReach) {             for (int j : g[i]) {               if (j == x || j == 0 ||                   binary_search(xReach.begin(), xReach.end(), j)) {                 continue;               }               y = j;               z = i;               break;             }             if (z >= 0) {               break;             }           }           assert(z >= 0);         }         cout << 5 << endl;         cout << 1 <<     << x + 1 <<     << z + 1 <<     << y + 1 <<     << x + 1              <<     << n << endl;         return 0;       }     }     if (ans1 == INT_MAX) {       cout << -1 << endl;       return 0;     }     cout << ans1 << endl;     vector<int> res;     int kur = n - 1;     while (kur >= 0) {       res.push_back(kur + 1);       kur = p[kur];     }     reverse(res.begin(), res.end());     for (int i : res) {       cout << i <<    ;     }     cout << endl;     return 0;   }   