#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],rasp[MAXN];
stack<int> st;

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

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]);
        }

    rasp[ctc].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])
            dfs_1(i);

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

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

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