#include<iostream>
#include<fstream>
#include<cmath>
#include<algorithm>
#include<vector>
#include<bitset>
#include<cstring>
#include<queue>
#include<stack>

#define ull unsigned long long
#define ll long long
#define pb push_back
#define FOR(a,b,c) for (int a=b;a<=c; ++a)
#define ROF(a,b,c) for (int a=b;a>=c; --a)

using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int N,M,nrcomp;
int a[5005][5005];
vector<int> v[5005];
vector<int> componente[5005];
bitset<5005> verif;

void dfs(int);

int main()
{
    f>>N>>M;
    FOR (i,1,M) {
        int x,y;
        f>>x>>y;
        a[x][y]=1;
    }
    FOR (i,1,N) {
        a[i][i]=1;
    }
    FOR (k,1,N) {
        FOR (i,1,N) {
            FOR (j,1,N) {
                a[i][j]=a[i][j] | (a[i][k] & a[k][j]);
            }
        }
    }
    FOR (i,1,N) {
        FOR (j,1,N) {
            if (a[i][j] && a[j][i]) {
                v[i].pb(j);
                v[j].pb(i);
            }
        }
    }
    FOR (i,1,N) {
        if (!verif.test(i)) {
            ++nrcomp;
            dfs(i);
        }
    }
    g<<nrcomp<<'\n';
    FOR (i,1,nrcomp) {
        vector<int>::iterator it;
        for (it=componente[i].begin();it<componente[i].end();++it) {
            g<<(*it)<<' ';
        }
        g<<'\n';
    }
    f.close();g.close();
    return 0;
}

void dfs(int nod) {
    verif.set(nod,1);
    componente[nrcomp].pb(nod);
    for (unsigned int k=0;k<v[nod].size();++k) {
        if (!verif.test(v[nod][k])) {
            dfs(v[nod][k]);
        }
    }
}