#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");

#define MAXN 100005

vector<int> g[MAXN], t[MAXN], ctc[MAXN];
stack<int> st;

int n,m,i,j,x,y,nod,nrctc;
bool fol[MAXN];

void dfs_1(int nod)
{
    for(int i=0; i<g[nod].size(); i++)
        if(!fol[ g[nod][i] ])
        {
            fol[ g[nod][i] ] = true;
            dfs_1( g[nod][i] );
        }

    st.push(nod);
}

void dfs_2(int nod)
{
    for(int i=0; i<t[nod].size(); i++)
        if(!fol[ t[nod][i] ])
        {
            fol[ t[nod][i] ] = true;
            dfs_2( t[nod][i] );
        }

    ctc[nrctc].push_back(nod);
}
int main()
{
    cin>>n>>m;
    for(i=1; i<=m; i++)
    {
        cin>>x>>y;
        g[x].push_back(y);
        t[y].push_back(x);
    }

    for(i=1; i<=n; i++)
        if(!fol[i])
        {
            fol[i]=true;
            dfs_1(i);
        }

    for(i=1; i<=n; i++)
        fol[i] = false;

    while(!st.empty())
    {
        nod=st.top(); st.pop();
        if(fol[nod])
            continue;

        nrctc++;
        fol[nod] = true;
        dfs_2(nod);
    }
    cout<<nrctc<<"\n";
    for(i=1; i<=nrctc; i++)
    {
        sort(ctc[i].begin(), ctc[i].end());
        for(j=0; j < ctc[i].size(); j++)
            cout<<ctc[i][j]<<" ";
        cout<<"\n";
    }
    return 0;
}