#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;
int nrsc;
bool is[NMAX];
int niv[NMAX], low[NMAX];
ifstream cin("scc.in");
ofstream cout("scc.out");
void scc(int nod)
{
    nrsc++;
    do
    {
        x = s.top();
        s.pop();
        sc[nrsc].push_back(x);
        is[x] = 0;
    }
    while(x!=nod);
}
void dfssc(int nod, int lvl)
{
    niv[nod] = low[nod] = lvl;
    s.push(nod);
    is[nod] = 1;
    for(int i = 0; i < G[nod].size(); i++)
    {
        int fiu = G[nod][i];
        if(niv[fiu] == 0)
        {
            dfssc(fiu, lvl + 1);
            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);
    }
}
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)
        {
            dfssc(i, 1);
        }
    }
    cout << nrsc << "\n";
    for(int i = 1; i <= nrsc; i++)
    {
        for(int j = 0; j < sc[i].size(); j++)
        {
            cout << sc[i][j] << " ";
        }
        cout << "\n";
    }
    return 0;
}