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

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

int n, m, in[256];
vector <int> g[256];

struct edge {
    int x, y;
};

vector <edge> add;
vector <int> r;

int dfs(int nod)
{
    r.push_back(nod);
    bool ok = false;
    int last = -1;

    for (auto& i : g[nod])
    {
        if (in[i] > 1)
        {
            in[i]--;
            continue;
        }

        ok = true;
        if (last != -1)
            add.push_back({ last, i });
        last = dfs(i);
    }

    if (last == -1)
        return nod;

    return last;
}

int main() {

    fin >> n >> m;

    for (int i = 1; i <= m; i++)
    {
        int x, y;
        fin >> x >> y;
        g[x].push_back(y);
        in[y]++;
    }

    int last = -1;

    for (int i = 1; i <= n; i++)
        if (!in[i])
        {
            if (last != -1)
                add.push_back({ last, i });
            last = dfs(i);
        }

    fout << add.size() << '\n';

    for (auto& i : add)
        fout << i.x << ' ' << i.y << '\n';

    for (auto& i : r)
        fout << i << ' ';
    
    return 0;

}