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

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

int n, m;
vector<vector<int>> adj_list, adj_list_trans;

vector<int> visited, scc;
stack<int> out;

vector<vector<int>> ans;

void read()
{
    fin >> n >> m;   

    adj_list.assign(n+1, {});
    adj_list_trans.assign(n+1, {});

    visited.assign(n+1, 0);

    for(int i=0; i<m; i++)
    {
        int x, y;
        fin >> x >> y;

        adj_list[x].push_back(y);
        adj_list_trans[y].push_back(x);
    }
}

void dfs(int x)
{       
    visited[x] = 1;
    for(auto &next:adj_list[x])
    {
        if(!visited[next])
            dfs(next);
    }
    out.push(x);      
}

void dfs_trans(int x)
{
    visited[x] = 1;
    scc.push_back(x);
    for(auto &next:adj_list_trans[x])
    {
        if(!visited[next])
            dfs_trans(next);
    }
}

void kosaraju()
{   
    for(int i=1; i<=n; i++)
        if(!visited[i])
            dfs(i);

    visited.assign(n+1, 0);

    while(!out.empty())
    {
        int curr = out.top();
        out.pop();

        if(visited[curr])
            continue;
        
        dfs_trans(curr);
        ans.push_back(scc);
        scc.clear();
    }    
}

int main()
{
    read();
    kosaraju();

    fout << ans.size() << '\n';
    for(auto &scc : ans)
    {
        for(auto &x:scc)
            fout << x << ' ';
        fout << '\n';
    }
        
    return 0;
}