#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream cin ("ctc.in");
ofstream cout ("ctc.out");
int n,m;
vector<int> aux;
bool u[100005];
vector<int> g[100005];
vector<int> gt[100005];
void dfs(int nod)
{
    u[nod] = true;
    for(auto x:g[nod])
    {
        if(u[x])
            continue;
        dfs(x);
    }
    aux.push_back(nod);
}
vector<int> componenta;
void dfst(int nod)
{
    u[nod] = true;
    componenta.push_back(nod);
    for(auto x:gt[nod])
    {
        if(u[x])
            continue;
        dfst(x);
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        cin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
    {
        if(u[i])
            continue;
        dfs(i);
    }
    reverse(aux.begin(),aux.end());
    for(int i=1;i<=n;i++)
        u[i] = false;
    vector<vector<int>> rasp;
    for(int i=0;i<aux.size();i++)
    {
        int vf = aux[i];
        if(u[vf])
            continue;
        componenta.clear();
        dfst(vf);
        rasp.push_back(componenta);
    }
    cout << rasp.size() << '\n';
    for(auto x:rasp)
    {
        for(auto y:x)
            cout << y << ' ';
        cout << '\n';
    }
    return 0;
}