#include <bits/stdc++.h>
#define nmax 100005
#define pb push_back
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m, indexat, depth[nmax], st[nmax], ss, numscc;
vector <int> graph[nmax];
vector <int> ctc[nmax];
bitset <nmax> vizat;

int strongcon(int v, int indexat)
{
    depth[v] = indexat;
    st[ss++] = v;
    vizat[v] = 1;
    unsigned i, len;
    len = graph[v].size();
    int vecin;
    for(i = 0; i < len; i++)
    {
        vecin = graph[v][i];
        if(depth[vecin] == 0)
            depth[v] = min(depth[v], strongcon(vecin, indexat + 1));
        else if(vizat[vecin])
            depth[v] = min(depth[v], depth[vecin]);
    }
    if(depth[v] == indexat)
    {
        do{
            vecin = st[--ss];
            vizat[vecin] = false;
            ctc[numscc].pb(vecin);
        }while(vecin != v);
        numscc++;
    }
    return depth[v];
}

int main()
{
    int i, x, y;
    fin >> n >> m;
    for(i = 0; i < m; i++)
        fin >> x >> y, graph[x].pb(y);
    for(i = 1; i <= n; i++)
        if(depth[i] == 0)
            strongcon(i, 1);
    fout << numscc << '\n';
    for(i = 0; i < numscc; i++)
    {
        x = ctc[i].size();
        for(y = x - 1; y >= 0; y--)
            fout << ctc[i][y] << ' ';
        fout << '\n';
    }
    return 0;
}