#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <string.h>

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

const int NMAX=100010;

int n,m;
vector<int> v[NMAX], vt[NMAX];
vector<vector<int>> ans;
stack<int> s;
bool viz[NMAX];

void dfs(int nod)
{
    viz[nod]=1;
    for(auto it:v[nod])
        if(!viz[it])
            dfs(it);
    s.push(nod);
}

void dfs2(int nod)
{
    viz[nod]=1;
    for(auto it:vt[nod])
        if(!viz[it])
            dfs2(it);
    ans.back().push_back(nod);
}

int main()
{
    int i,x,y;
    fin>>n>>m;
    for(i=0; i<m; i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }

    for(i=1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    memset(viz, 0, sizeof(viz));

    while(!s.empty())
    {
        i=s.top();
        s.pop();
        if(!viz[i])
        {
            ans.push_back(vector<int>());
            dfs2(i);
        }
    }

    fout<<ans.size()<<'\n';
    for(auto it:ans)
    {
        for(auto jt:it)
            fout<<jt<<' ';
        fout<<'\n';
    }
    return 0;
}