#include <cstdio>
#include <algorithm>
#include <vector>
#include <iostream>

using namespace std;

const int N=100000+5;

int n,m;
vector<int>g1[N],g2[N];

bool viz[N];
vector<int>ord;

inline void dfs1(int nod)
{
    viz[nod]=1;
    for(auto &nou:g1[nod])
    {
        if(viz[nou]==0)
        {
            dfs1(nou);
        }
    }
    ord.push_back(nod);
}

vector<vector<int>>ans;

inline void dfs2(int nod)
{
    viz[nod]=1;
    ans.back().push_back(nod);
    for(auto &nou:g2[nod])
    {
        if(viz[nou]==0)
        {
            dfs2(nou);
        }
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        g1[x].push_back(y);
        g2[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            dfs1(i);
        }
    }
    for(int i=1;i<=n;i++)
    {
        viz[i]=0;
    }
    reverse(ord.begin(),ord.end());
    for(auto &nod:ord)
    {
        if(viz[nod]==0)
        {
            ans.push_back({});
            dfs2(nod);
        }
    }
    cout<<ans.size()<<"\n";
    for(auto &i:ans)
    {
        for(auto &j:i)
        {
            cout<<j<<" ";
        }
        cout<<"\n";
    }
    return 0;
}