#include <fstream>
#include <vector>
using namespace std;
ifstream cin ("ctc.in");
ofstream cout ("ctc.out");
int n,m;
vector<int> g[100005];
vector<int> gt[100005];
vector<int> st;
int cnt;
vector<int> comp[100005];
bool u[100005];
void dfs(int nod)
{
    u[nod] = true;
    for(auto urm:g[nod])
    {
        if(u[urm])
            continue;
        dfs(urm);
    }
    st.push_back(nod);
}
void dfs2(int nod)
{
    u[nod] = true;
    comp[cnt].push_back(nod);
    for(auto urm:gt[nod])
    {
        if(u[urm])
            continue;
        dfs2(urm);
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for(int i=1;i<=m
    ;i++)
    {
        int x,y;
        cin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
    {
        if(u[i])
            continue;
        dfs(i);
    }
    for(int i=1;i<=n;i++)
        u[i] = false;
    while(!st.empty())
    {
        int vf = st.back();
        st.pop_back();
        if(u[vf])
            continue;
        cnt++;
        dfs2(vf);
    }
    cout << cnt << '\n';
    for(int i=1;i<=cnt;i++)
    {
        for(auto x:comp[i])
            cout << x << ' ';
        cout << '\n';
    }
    return 0;
}