#include<fstream>
#include<vector>
#include<stack>
#define NMAX 100005
using namespace std;

vector<int> G[NMAX], sc[NMAX];

stack<int> s;

int n, m, x, y, i, j;

int nrsc, lvl;

int niv[NMAX], low[NMAX];

bool u[NMAX];

ifstream _cin("ctc.in");
ofstream _cout("ctc.out");
void scc(int nod)
{
    nrsc++;
    do
    {
        x = s.top();
        s.pop();
        u[x] = 0;
        sc[nrsc].push_back(x);
    }while(x != nod);
}
void dfssc(int nod)
{
    niv[nod] = low[nod] = ++lvl;
    s.push(nod);
    u[nod] = 1;
    for(int i = 0; i < G[nod].size(); i++)
    {
        int fiu = G[nod][i];
        if(niv[fiu] == 0)
        {
            dfssc(fiu);
            low[nod] = min(low[fiu], low[nod]);
        }else
        {
            if(u[fiu] == 1)
            {
                low[nod] = min(low[fiu], low[nod]);
            }
        }
    }
    if(low[nod] == niv[nod])
    {
        scc(nod);
    }
}
void afisare()
{
    _cout << nrsc << "\n";
    for(i = 1; i <= nrsc; i++)
    {
        for(j = 0; j < sc[i].size(); j++)
        {
            _cout << sc[i][j] << " ";
        }
        _cout << "\n";
    }
}
int main()
{
    _cin >> n >> m;
    for(i = 1; i <= m; i++)
    {
        _cin >> x >> y;
        G[x].push_back(y);
    }
    for(i = 1; i <= n; i++)
    {
        if(niv[i] == 0)
        {
            dfssc(i);
        }
    }
    afisare();
    return 0;
}