func_code_string: #include <bits/stdc++.h>   using namespace std;   int vis[100005], mark[100005];   vector<int> g[100005];   int prob = 0;   void dfs(int node, int k) {     mark[node] = k;     vis[node] = 1;     for (auto i : g[node]) {       if (!vis[i]) {         dfs(i, 1 - k);       } else {         if (mark[i] == k) {           prob = 1;         }       }     }   }   int main() {     int n, m;     cin >> n >> m;     for (int i = 0; i < m; i++) {       int u, v;       scanf( %d , &u);       scanf( %d , &v);       g[u].push_back(v);       g[v].push_back(u);     }     for (int i = 1; i <= n; i++) {       if (!vis[i]) dfs(i, 0);     }     if (prob) {       cout <<  -1 ;       return 0;     }     int k = 0;     for (int i = 1; i <= n; i++) {       if (mark[i] == 1) k++;     }     cout << k <<   n ;     for (int i = 1; i <= n; i++) {       if (mark[i] == 1) cout << i <<    ;     }     cout <<   n ;     k = 0;     for (int i = 1; i <= n; i++) {       if (mark[i] == 0) k++;     }     cout << k <<   n ;     for (int i = 1; i <= n; i++) {       if (mark[i] == 0) cout << i <<    ;     }     return 0;   }   