func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<int> e[200005], E[200005], v;   int vis[200005];   inline void dfs(int u) {     if (vis[u]) return;     vis[u] = 1;     v.push_back(u);     int x = E[u][0], y = E[u][1];     if (e[x][0] == e[u][0] || e[x][0] == e[u][1] || e[x][1] == e[u][1] ||         e[x][1] == e[u][0])       dfs(x);     dfs(y);   }   int main(int argc, char** argv) {     int n;     cin >> n;     for (int i = 1; i <= n; i++) {       int x, y;       cin >> x >> y;       e[i].push_back(y);       e[i].push_back(x);       E[x].push_back(i);       E[y].push_back(i);     }     dfs(1);     for (int i = v.size() - 1; i >= 0; i--) cout << v[i] <<    ;     return 0;   }   