#include <iostream>
#include <bits\stdc++.h>
#define N 100005
using namespace std;
vector<int> G[N],GT[N];
vector<vector<int>> CTC;
int viz[N];
int n,m;
stack <int> S;



void citire()
{
    cin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        cin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }

}

void dfs1(int nod)
{
    viz[nod]=1;
    for(auto vecin:G[nod])
        if(!viz[vecin])
            dfs1(vecin);
    S.push(nod);
}




void dfs2(int nod)
{
    viz[nod]=1;
    CTC.back().push_back(nod);
    for(auto vecin:GT[nod])
        if(!viz[vecin])
            dfs2(vecin);
}


int main() {

    citire();

    for(int i=1;i<=n;i++)
        if(!viz[i])
            dfs1(i);

    memset(viz,0,sizeof(viz));

    while(!S.empty())
    {
        int nod=S.top();
        S.pop();
        if(!viz[nod])
        {
            CTC.push_back(vector<int>());
            dfs2(nod);
        }
    }
    cout<<CTC.size()<<endl;
    for(auto comp:CTC)
    {
        for(auto nod:comp)
            cout<<nod<<" ";
        cout<<endl;
    }



    return 0;
}