#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

const int knmax = 100005;

int n, m;
vector<int> graph[knmax];
vector<vector<int> > ans;

void read(){
    ifstream in("ctc.in");

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

bool vis[knmax], instk[knmax];
int ind[knmax], dp[knmax];
vector<int> stk;
int index;

void dfs(int x){
    vis[x] = true;
    ind[x] = index;
    dp[x] = index;
    ++index;
    stk.push_back(x);
    instk[x] = true;

    for(int i = 0; i < graph[x].size(); ++i)
        if(!vis[graph[x][i]]) {
            dfs(graph[x][i]);
            dp[x] = min(dp[x], dp[graph[x][i]]);
        } else if (instk[graph[x][i]])
            dp[x] = min(dp[x], ind[graph[x][i]]);

    if(ind[x] == dp[x]) {
        vector<int> add;
        while(stk.back() != x) {
            add.push_back(stk.back());
            instk[stk.back()] = false;
            stk.pop_back();
        }
        add.push_back(stk.back());
        instk[stk.back()] = false;
        stk.pop_back();
        ans.push_back(add);
    }
}

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

void write(){
    ofstream out("ctc.out");

    out << ans.size() << "\n";
    for(int i = 0; i < ans.size(); ++i){
        for(int j = 0; j < ans[i].size(); ++j)
            out << ans[i][j] << " ";
        out << "\n";
    }
}

int main () {
    read();
    solve();
    write();
}