#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#define NMAX 100005

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

int n,m,x,y,d[NMAX],viz[NMAX],contor,componenta;
vector<int> a[NMAX];
vector<int> t[NMAX];
vector<int> sol[NMAX];

void dfs(int nod) {
    viz[nod] = 1;

    for(int i=0;i<a[nod].size();i++) {
        if(!viz[a[nod][i]]) {
            dfs(a[nod][i]);
        }
    }

    d[contor++] = nod;
}

void dfst(int nod) {
    viz[nod] = 1;

    for(int i=0;i<t[nod].size();i++) {
        if(!viz[t[nod][i]]) {
            dfst(t[nod][i]);
        }
    }
    sol[componenta].push_back(nod);
}

int main()
{
    in >> n >> m;

    for(int i=0;i<m;i++) {
        in >> x >> y;
        a[x].push_back(y);
        t[y].push_back(x);
    }

//    for(int i=1;i<=n;i++) {
//        for(int j=0;j<a[i].size();j++) {
//            cout << i << "->>> " << a[i][j] << " ";
//        }
//        cout << endl;
//    }

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

    for(int i=1;i<=n;i++) {
        viz[i] = 0;
    }

    for(int i=n-1;i>=0;i--) {
        if(!viz[d[i]]) {
            dfst(d[i]);
            //cout << d[i] << " ";
            componenta++;
            //cout << 1 << " ";
        }
    }

    out << componenta << "\n";
    for(int i=0;i<componenta;i++) {
        sort(sol[i].begin(),sol[i].end());
        for(int j=0;j<sol[i].size();j++) {
            out<< sol[i][j] << " ";
        }
        out << "\n";
    }

    return 0;
}