#include <bits/stdc++.h>

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

int n, m, l, sol;
pair<int, int> p[100005];
vector<int> graph[100005], out[100005];
stack<int> stk;
bitset<100005> check, inS;

void dfs(int now);

int main()
{

    fin >> n >> m;
    while(m--){
        int x, y;
        fin >> x >> y;

        graph[x].push_back(y);
    }

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

    fout << sol << "\n";
    for(int i = 1; i <= sol; ++i){
        for(auto it:out[i]) fout << it << " ";
        fout << "\n";
    }

    return 0;
}

void dfs(int now){
    ++l;
    p[now] = {l, l};
    check[now] = inS[now] = true;
    stk.push(now);

    for(auto next:graph[now]){
        if(!check[next]){
            dfs(next);
            p[now].second = min(p[now].second, p[next].second);
        }
        else if(inS[next]) p[now].second = min(p[now].second, p[next].second);
    }

    if(p[now].first == p[now].second){
        ++sol;

        while(stk.top() != now){
            out[sol].push_back(stk.top());
            inS[stk.top()] = false;
            stk.pop();
        }

        out[sol].push_back(stk.top());
        inS[stk.top()] = false;
        stk.pop();
    }

}