#include <bits/stdc++.h>
#define nmax 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
bool vizat1[nmax], vizat2[nmax];
vector <int> graph1[nmax];
vector <int> graph2[nmax];
vector <int> ctc[nmax];
stack <int> ord;
int n, m, ctc_size;

void dfs1(int nod)
{
    vizat1[nod] = 1;
    unsigned len, i;
    int var;
    len = graph1[nod].size();
    for(i = 0; i < len; i++)
    {
        var = graph1[nod][i];
        if(!vizat1[var])
            dfs1(var);
    }
    ord.push(nod);
}

void dfs2(int nod)
{
    vizat2[nod] = 1;
    unsigned len, i;
    int var;
    len = graph2[nod].size();
    for(i = 0; i < len; i++)
    {
        var = graph2[nod][i];
            if(!vizat2[var])
                dfs2(var);
    }
    ctc[ctc_size].push_back(nod);
}

int main()
{
    int i, x, y;
    unsigned j, len;
    fin >> n >> m;
    for(i = 0; i < m; i++)
    {
        fin >> x >> y;
        graph1[x].push_back(y);
        graph2[y].push_back(x);
    }
    for(i = 1; i <= n; i++)
        if(!vizat1[i])
            dfs1(i);
    while(!ord.empty())
    {
        x = ord.top();
        ord.pop();
        if(!vizat2[x])
        {
            dfs2(x);
            ctc_size++;
        }
    }
    fout << ctc_size << endl;
    for(i = 0; i < ctc_size; i++)
    {
        len = ctc[i].size();
        for(j = 0; j < len; j++)
            fout << ctc[i][j] << ' ';
        fout << '\n';
    }
    return 0;
}