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

using namespace std;

bool vis[50005];
vector<int> G[50005];
vector<int> Gt[50005];
stack<int> st;

vector<int> temp;
vector<vector<int>> res;

void dfs(int i)
{
    vis[i] = 1;

    for(int x : G[i])
    {
        if(vis[x] == 0)
            dfs(x);
    }

    st.push(i);
}

void dfs2(int i)
{
    vis[i] = 1;

    temp.push_back(i);

    for(int x : Gt[i])
    {
        if(vis[x] == 0)
            dfs2(x);
    }
}

int main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");

    int n, m, x, y;
    cin >> n >> m;
    for(int i=0;i<m;i++)
    {
        cin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }

    for(int i=1;i<=n;i++)
    {
        if(vis[i] == 0)
            dfs(i);
    }

    for(int i=0;i<=50000;i++)
        vis[i] = 0;

    while(!st.empty())
    {
        int i = st.top();
        if(vis[i] == 0)
        {
            dfs2(i);

            res.push_back(temp);
            temp.clear();
        }
        st.pop();
    }

    cout << res.size() << '\n';
    for(auto i: res)
    {
        for(int j:i)
            cout << j << " ";
        cout << '\n';
    }
    return 0;
}