SPOJ BIA

#define ll long long
#include <bits/stdc++.h>
using namespace std;

const int OO = 1e9;
const double EPS = 1e-9;

vector<vector<int>> graph;
int n,m;
vector<bool> vis;
int v_cnt = 0;

void dfs(int curr, int ex) {
    vis[curr] = 1;
    v_cnt++;
    for(int e : graph[curr]) {
        if(e != ex && !vis[e]) {
            dfs(e,ex);
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 10;
    while(t--) {
        cin >> n >> m;
        graph.clear();
        graph.resize(n);
        vis.resize(n);
        for(int i = 0; i < m; i++) {
            int a,b;
            cin >> a >> b;
            a--,b--;
            graph[a].push_back(b);
        }
        vector<int> ans;
        for(int i = 0; i < n; i++) {
            vis.assign(n,0);
            v_cnt = 0;
            dfs(0,i);
            if(v_cnt != n-1) {
                ans.push_back(i+1);
            }
        }
        cout << ans.size() << "\n";
        for(int i = 0; i < ans.size(); i++) {
            if(i)
                cout << " ";
            cout << ans[i];
        }
        cout << "\n";
    }

    return 0;
}