#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

int n;
vector<int> g[100000];
map<pair<int, int>, int> idx;
int vis[100000];
stack<int> stk;
vector<int> ret;

void dfs(int v, int p = -1) {
  vis[v] = -1;
  stk.push(v);
  
  for (int w : g[v]) {
    if (w == p) continue;
    if (vis[w] == 1) continue;
    if (vis[w] == -1) {
      while (stk.top() != w) {
        ret.push_back(stk.top());
        stk.pop();
      }
      for (int i = ret.size() - 1; i >= 0; i--)
        stk.push(ret[i]);
      ret.push_back(w);
    } else {
      dfs(w, v);
    }
  }
  stk.pop();
  vis[v] = 1;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  cin >> n;
  for (int i = 0; i < n; i++) {
    int a, b;
    cin >> a >> b;
    --a, --b;
    idx[make_pair(min(a, b), max(a, b))] = i + 1;
    g[a].push_back(b);
    g[b].push_back(a);
  }

  dfs(0);

  int m = ret.size();
  cout << m << endl;
  for (int i = 0; i < m; i++) {
    int a = ret[i];
    int b = ret[(i+1)%m];
    cout << idx[make_pair(min(a, b), max(a,b))] << " ";
  }
  cout << endl;
  
  return 0;
}