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

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

int n, m, numComponents=1;
vector <int> og[NMAX], tg[NMAX];
stack <int> st;
bool visited[NMAX];

//int component[NMAX];
vector <int> components[NMAX];

void dfs_1(int x)
{
    visited[x]=true;
    for(int i: og[x])
        if(!visited[i]) dfs_1(i);
    st.push(x);
}

void dfs_2(int x)
{
    //cout<<x<<" ";
    //component[x] = numComponents;
    components[numComponents].push_back(x);
    visited[x]=true;
    for(int i: tg[x])
        if(!visited[i]) dfs_2(i);
}

void Kosaraju()
{
    for(int i=1; i<=n; i++)
        if(!visited[i]) dfs_1(i);
    for(int i=1; i<=n; i++)
        visited[i]=false;
    while (!st.empty())
    {
        int v=st.top();
        st.pop();
        if (!visited[v])
        {
            dfs_2(v);
            numComponents++;
            //printf("\n");
        }
    }
}

int main()
{
    fin>>n>>m;
    int a, b;
    for(int i=1; i<=m; ++i)
    {
        fin>>a>>b;
        og[a].push_back(b);
        tg[b].push_back(a);
    }
    Kosaraju();
    fout<<numComponents-1<<endl;
    for(int i=1; i<=numComponents; ++i, fout<<endl)
        for(int j: components[i])
            fout<<j<<" ";
    return 0;
}