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

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
int n, m , nrcc;
vector <int> T[nmax];
vector <int> L[nmax];
vector <int> sol[nmax];
bitset <nmax> viz;
stack <int> st;

void Read()
{
    int x, y;
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        L[x].push_back(y);
        T[y].push_back(x);
    }
}

void DFS1(int k)
{
    viz[k] = 1;
    for(auto i : L[k])
        if(viz[i] == 0)
            DFS1(i);
    st.push(k);
}

void DFS2(int k)
{
    viz[k] = 1;
    sol[nrcc].push_back(k);
    for(auto i : T[k])
        if(viz[i] == 0)
            DFS2(i);
}
void Print()
{
    fout << nrcc << "\n";
    for(int i = 1;i <= nrcc; i++)
    {
        for(auto j : sol[i])
            fout << j << " ";
        fout << "\n";
    }
}
void Do()
{
    int cNode;
    for(int i = 1; i <= n; i++)
        if(viz[i] == 0)
            DFS1(i);
    viz.reset();
    while(!st.empty())
    {
        cNode = st.top();
        st.pop();
        if(viz[cNode] == 0)
        {
            nrcc++;
            DFS2(cNode);
        }
    }
    Print();
}
int main()
{
    Read();
    Do();
    return 0;
}