#include <fstream>
#include <vector>
#include <stack>

#define N 100005

using namespace std;

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

int n;
bool viz[N];
vector <int> G[N], GT[N], sol[N];
stack <int> st;
int nrcomp;

void DFS(int x)
{
    viz[x] = 1;
    for(int i = 0; i < G[x].size(); ++i)
        if(!viz[G[x][i]]) DFS(G[x][i]);
    st.push(x);
}

void DFST(int x)
{
    viz[x] = 0;
    sol[nrcomp].push_back(x);
    for(int i = 0; i < GT[x].size(); ++i)
        if(viz[GT[x][i]]) DFST(GT[x][i]);
}


int main()
{
    int m;
    fin >> n >> m;
    for(int i = 1, x, y; i <= m; ++i)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    fin.close();

    for(int i = 1; i <= n; ++i)
        if(!viz[i]) DFS(i);
    while(!st.empty())
    {
        int x = st.top();
        if(viz[x])
        {
            DFST(x);
            nrcomp++;
        }
        st.pop();
    }

    fout << nrcomp << '\n';
    for(int i = 0; i < nrcomp; ++i)
    {
        for(int j = 0; j < sol[i].size(); ++j) fout << sol[i][j] << " ";
        fout << '\n';
    }
    return 0;
}