func_code_string: #include <bits/stdc++.h>   using namespace std;   void inout() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     ;   }   int main() {     inout();     long long n, i, u, v;     cin >> n;     map<long long, long long> prv, nxt, cnt1, cnt2;     vector<long long> ans(n + 5);     for (i = 0; i < n; i++) {       cin >> u >> v;       prv[v] = u;       nxt[u] = v;       cnt1[u]++;       cnt2[v]++;     }     for (auto k : cnt1)       if (cnt1[k.first] > cnt2[k.first]) ans[1] = k.first;     for (auto k : cnt2)       if (cnt1[k.first] < cnt2[k.first]) ans[n] = k.first;     i = 3;     while (i <= n) {       ans[i] = nxt[ans[i - 2]];       i += 2;     }     i = n + n % 2 - 2;     while (i > 0) {       ans[i] = prv[ans[i + 2]];       i -= 2;     }     for (i = 1; i <= n; i++) cout << ans[i] <<    ;     return 0;   }   