#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

using namespace std;

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

const int N = 255;

int n, m;
bool edge[N + 5][N + 5], fr[N + 5];
stack<int> s;
vector<int> adj[N + 5], ans;
vector<pair<int, int>> add;

void dfs(int node) {
    fr[node] = true;
    for (auto it: adj[node])
        if (!fr[it])
            dfs(it);
    s.push(node);
}

int main() {
    in >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        in >> x >> y;
        adj[x].push_back(y);
        edge[x][y] = true;
    }
    for (int i = 1; i <= n; i++)
        if (!fr[i])
            dfs(i);
    while (!s.empty()) {
        ans.push_back(s.top());
        s.pop();
    }
    for (int i = 0; i < ans.size() - 1; i++) {
        int x = ans[i], y = ans[i + 1];
        if (!edge[x][y])
            add.emplace_back(x, y);
    }
    out << add.size() << '\n';
    for (auto it: add)
        out << it.first << ' ' << it.second << '\n';
    for (auto it: ans)
        out << it << ' ';
    out << '\n';
    return 0;
}