#include<fstream>
#include<vector>
#include<stack>
#define NMAX 100005
using namespace std;
vector<int> G[NMAX], st[NMAX];
stack<int> s;
int n, m, x, y;
int lvl;
int niv[NMAX], low[NMAX];
int nst;
bool is[NMAX];
ifstream _cin("ctc.in");
ofstream _cout("ctc.out");

void scc(int nod)
{
    nst++;
    do
    {
        x = s.top();
        s.pop();
        is[x] = 0;
        st[nst].push_back(x);
    }
    while(x != nod);
}

void dfsst(int nod)
{
    s.push(nod);
    is[nod] = 1;

    niv[nod] = low[nod] = ++lvl;

    for(int i = 0; i < G[nod].size(); i++)
    {
        int fiu = G[nod][i];
        if(niv[fiu] == 0)
        {
            dfsst(fiu);
            low[nod] = min(low[fiu], low[nod]);
        }else
        {
            if(is[fiu])
            {
                low[nod] = min(low[fiu], low[nod]);
            }
        }
    }
    if(low[nod] == niv[nod])
    {
        scc(nod);
    }
}

void afisare()
{
    _cout << nst << "\n";
    for(int i = 1; i <= nst; i++)
    {
        for(int j = 0; j < st[i].size(); j++)
        {
            _cout << st[i][j] << " ";
        }
        _cout << "\n";
    }
}

int main()
{
    _cin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        _cin >> x >> y;
        G[x].push_back(y);
    }

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

    afisare();
    return 0;
}