#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define ld long double
#define chad char
#define mod 1'000'000'007
#define dim 100005
#define lim 1000000
#define INF 1000000000
#define FOR(i,a,b) for(int i=(a); i<=(b); i++)
#define piii pair<int,pair<int,int> > 
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define mp make_pair
#define nr_biti __builtin_popcount
using namespace std;
 
ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n,m;

vector<int> g[dim],gt[dim];
bool viz[dim];
stack<int> d;

void dfs1(int nod)
{
    viz[nod]=1;

    for(auto it:g[nod])
        if(!viz[it])
            dfs1(it);
    
    d.push(nod);
}

vector<vector<int> > v;
vector<int> aux;

void dfs2(int nod)
{
    viz[nod]=1;
    aux.pb(nod);

    for(auto it:gt[nod])
        if(!viz[it])
            dfs2(it);
}

int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(nullptr);
    fout.tie(nullptr); 

    fin >> n >> m;

    for(int i=1; i<=m; i++)
    {
        int x,y;

        fin >> x >> y;

        g[x].pb(y);
        gt[y].pb(x);
    }

    for(int i=1; i<=n; i++)
        if(!viz[i])
            dfs1(i);

    memset(viz,0,sizeof(viz));

    while(d.size())
    {
        int x=d.top();
        d.pop();

        if(!viz[x])
        {
            aux.clear();
            dfs2(x);
            v.pb(aux);
        }
    }

    fout << v.size() << "\n";

    for(auto it:v)
    {
        for(auto i:it)
            fout << i << " ";

        fout << "\n";
    }

    return 0;
}