#include <fstream>
#include <vector>
#include <queue>

using namespace std;

ifstream in ("strazi.in");
ofstream out ("strazi.out");

const int max_size = 256;

int vizitat[max_size], inc[max_size], last;
vector <int> edges[max_size], ans, st;
vector <pair <int,int>> muchii;
queue <int> coada;

void dfs (int nod)
{
    vizitat[nod] = 1;
    ans.push_back(nod);
    if (edges[nod].size() == 0)
    {
        last = nod;
    }
    if (edges[nod].size() == 1)
    {
        dfs(edges[nod][0]);
    }
    if (edges[nod].size() > 1)
    {
        dfs(edges[nod][0]);
        for (int i = 1; i < edges[nod].size(); i++)
        {
            muchii.push_back(make_pair(last, edges[nod][i]));
            dfs(edges[nod][i]);
        }
    }
}

int main ()
{
    int n, t;
    in >> n >> t;
    while (t--)
    {
        int x, y;
        in >> x >> y;
        edges[x].push_back(y);
        inc[y] = 1;
    }
    for (int i = 1; i <= n; i++)
    {
        if (inc[i] == 0)
        {
            coada.push(i); /// fac DFS pt fiecare nod care nu are muchie de in
            /// repr gen radacina unui subarb maxim din comp conexa din graf
        }
    }
    /// fac o pseudo muchie pt primul subarbore
    while (!coada.empty())
    {
        muchii.push_back(make_pair(last, coada.front()));
        dfs(coada.front());
        coada.pop();
    }
    out << muchii.size() - 1 << '\n';
    for (int i = 1; i < muchii.size(); i++)
    {
        out << muchii[i].first << " " << muchii[i].second << '\n';
    }
    for (auto f : ans)
    {
        out << f << " ";
    }
    in.close();
    out.close();
    return 0;
}