#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

int n, m;
vector<int> graf[100005], grafInvers[100005];
bool viz1[100005], viz2[100005];
stack<int> S;
vector<int> currSol;
vector<vector<int> > sol;

void read()
{
    int x, y;
    f>>n>>m;
    for(int i = 0; i<m; ++i)
    {
        f>>x>>y;
        graf[x].push_back(y);
        grafInvers[y].push_back(x);
    }
}

void dfs(int node)
{
    viz1[node] = true;
    for(int nd : graf[node])
    {
        if(!viz1[nd])
        {
            dfs(nd);
        }
    }
    S.push(node);
}

void dfsInvers(int node)
{
    viz2[node] = true;
    for(int nd : grafInvers[node])
    {
        if(!viz2[nd])
        {
            dfsInvers(nd);
        }
    }
    currSol.push_back(node);
}

void solve()
{
    for(int i = 1; i<=n; ++i)
    {
        if(!viz1[i])
            dfs(i);
    }
    while(!S.empty())
    {
        int i = S.top();
        S.pop();
        if(!viz2[i])
        {
            dfsInvers(i);
            sol.push_back(currSol);
            currSol.clear();
        }
    }
}

void print()
{
    g<<sol.size()<<"\n";
    for(auto p : sol)
    {
        for(int nod : p)
        {
            g<<nod<<" ";
        }
        g<<"\n";
    }
}

int main()
{
    read();
    solve();
    print();
    return 0;
}