#include <fstream>
#include <vector>
#include <algorithm>
#include <bitset>

using namespace std;

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

const int N = 100000;

vector<vector<int>> graf;
vector<vector<int>> graft;
vector<vector<int>> ctc;
vector<int> s;

bitset<N + 1> viz;
int n, m, nrc = 0;

void Init()
{
    in >> n >> m;
    graf = graft = vector<vector<int>> (n + 1);
    for(int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;
        graf[x].push_back(y);
        graft[y].push_back(x);
    }
}

void Dfs1(int x)
{
    viz[x] = true;
    for(auto y : graf[x])
    {
        if(!viz[y])
        {
            Dfs1(y);
        }
    }
    s.push_back(x);
}

void Dfs2(int x, vector<int> &vec)
{
    viz[x] = true;
    vec.push_back(x);
    for(auto y : graft[x])
    {
        if(!viz[y])
        {
            Dfs2(y, vec);
        }
    }
}

int main()
{
    Init();
    viz.reset();
    for(int i = 1; i <= n; i++)
    {
        if(!viz[i])
        {
            Dfs1(i);
        }
    }
    viz.reset();
    reverse(s.begin(), s.end());
    for(auto y : s)
    {
        if(!viz[y])
        {
            vector<int> tmp;
            Dfs2(y, tmp);
            ctc.push_back(tmp);
        }
    }
    out << ctc.size() << "\n";
    for(auto vec : ctc)
    {
        for(auto y : vec)
        {
            out << y << " ";
        }
        out << "\n";
    }

    in.close();
    out.close();
    return 0;
}