#include <fstream>
#include <vector>
#include <queue>
#include <cstring>
#define NMAX 100005
#define MMAX 200005

using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");

vector <int> adj[NMAX];
vector <int> rev_adj[NMAX];
vector <int> cnx[NMAX];
int viz[NMAX], cmp_cnx;
int stiva[NMAX], cnt;
bool cmp[NMAX];

void dfs1(int node)
{
    viz[node] = 1;
    int i;
    for (i = 0; i < adj[node].size(); ++i)
    {
        int vecin = adj[node][i];
        if (viz[vecin] == 0)
        {
            dfs1(vecin);
        }
    }
    stiva[++cnt] = node;
}

void dfs2(int node)
{
    cnx[cmp_cnx].push_back(node);
    cmp[node] = 1;
    int i;
    for (i = 0; i < rev_adj[node].size(); ++i)
    {
        int vecin = rev_adj[node][i];
        if (cmp[vecin] == 0)
            dfs2(vecin);
    }
}

int main()
{
    int n, m, i, j, a, b;
    in >> n >> m;
    for (i = 1; i <= m; ++i)
    {
        in >> a >> b;
        adj[a].push_back(b);
        rev_adj[b].push_back(a);
    }

    for (i = 1; i <= n; ++i)
    {
        if (viz[i] == 0)
        {
            dfs1(i);
        }
    }

    while(cnt)
    {
        if (cmp[stiva[cnt]] == 0)
        {
            ++cmp_cnx;
            dfs2(stiva[cnt]);
        }
        cnt--;
    }

    out << cmp_cnx << '\n';
    for (i = 1; i <= cmp_cnx; ++i)
    {
        for (j = 0; j < cnx[i].size(); ++j)
            out << cnx[i][j] << " ";
        out << '\n';
    }
    return 0;
}