#include <bits/stdc++.h>

using namespace std;

#define INFILE "ctc.in"
#define OUTFILE "ctc.out"

const int N_MAX = 1e5 + 5;

int n, m;
int currentCTC = 0;
bool visited[N_MAX];
stack<int> st;
vector<int> ctc[N_MAX];
vector<int> adj[N_MAX], revAdj[N_MAX];

void dfs(int node){
    visited[node] = true;
    for(auto &to : adj[node]){
        if(!visited[to]) dfs(to);
    }
    st.push(node);
}

void revDfs(int node){
    visited[node] = false;
    ctc[currentCTC].push_back(node);
    for(auto &to : revAdj[node]){
        if(visited[to]) revDfs(to);
    }
}

void kosaraju(){

    for(int node = 1; node <= n; ++node){
        if(!visited[node]) dfs(node);
    }

    while(!st.empty()){
        if(visited[st.top()]){
            ++currentCTC;
            revDfs(st.top());
        }
        st.pop();
    }

}

void solve(){

    cin >> n >> m;
    for(int i = 0; i < m; ++i){
        int node1, node2; cin >> node1 >> node2;
        adj[node1].push_back(node2);
        revAdj[node2].push_back(node1);
    }

    kosaraju();

    cout << currentCTC << '\n';
    for(int i = 1; i <= currentCTC; ++i){
        for(int &it : ctc[i]) cout << it << " ";
        cout << '\n';
    }

}

int main(){
    ios_base::sync_with_stdio(false);
    freopen(INFILE, "r", stdin);
    freopen(OUTFILE, "w", stdout);
    cin.tie(0), cout.tie(0);
    solve();
    return 0;
}