#include <bits/stdc++.h>
using namespace std;
vector<vector<int> > a;
int n, m, cnt(0), res;
bool visit[1001];
vector<int> b;
deque<int> s;
void DFS(int u)
{
    visit[u]=true;
    s.push_back(u);
    for(int i=0;i<a[u].size();i++)
    {
        int v=a[u][i];
        if(!visit[v])
        {
            DFS(v);
            low[u]=min(low[u],low[v]);
        }
        else{
            low[u]=min(low[u],id[v]);
            if(find(s.begin(),s.end(),v) != s.end())
            {
                vector<int> c;
                while(true)
                {
                    int x = s.back();
                    c.push_back(x);
                    if(x == v) break;
                    s.pop_back();
                }
                if(c.size() > b.size()) b = c;

            }
        }
    }
}

void enter(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    freopen("GIANGHO.INP","r",stdin);
    freopen("GIANGHO.OUT","w",stdout);

    cin>>n;

    a.resize(n+1);

    int x,y;
    while(cin>>x>>y)
        a[x].push_back(y);
}

int main()
{
    enter();

    for(int i=1;i<=n;i++)
        if(!visit[i])
            DFS(i);
    cout<<b.size()<<endl;
    for(x : b) cout<<x<<" ";
    return 0;
}