#include <fstream>
#include <vector>
#include <stack>
#include <iostream>
using namespace std;
vector<int> v[100001];
vector<int> t[100001];
bool visited[100001];
stack<int> s;
int n, m;
ifstream in ("ctc.in");
ofstream out ("ctc.out");
vector <vector<int> > ans;
void dfs_normal (int node)
{
    if (visited[node] == 1)
        return;

    for (auto vecin : t[node])
    {
        s.push(vecin);
        visited[vecin] = 1;
        dfs_normal(vecin);
    }
}
void dfs_invers (int node, int comp)
{
    cout << node << ' ' << comp << '\n';
    if (visited[node] == 1)
        return;

    ans[comp].push_back(node);
    visited[node] = 1;
    for (auto vecin : v[node])
        dfs_invers(vecin, comp);
}
int main () {
    in >> n >> m;
    for (int i = 0; i < m; ++i)
    {
        int a, b;
        in >> a >> b;
        v[a].push_back(b);
        t[b].push_back(a);
    }

    for (int i = 1; i <= n; ++i)
    {
        if (visited[i] == 0)
            dfs_normal(i);
    }
    for (int i = 1; i <= n; ++i)
        visited[i] = 0;
    int comps = 0;
    while (!s.empty())
    {
        int node = s.top();
        s.pop();
        if (visited[node] == 0)
        {
            vector<int> e;
            ans.push_back(e);
            dfs_invers(node, comps++);
        }
    }
    out << ans.size() << '\n';
    for (auto vv : ans)
    {
        for (auto num : vv)
            out << num << ' ';
        out << '\n';
    }
}