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

using namespace std;

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

const int NMAX = 100000;

vector<int> g[1+NMAX];
vector<int> gT[1+NMAX];
vector<int> sorted;
bool visited[1+NMAX],visitedT[1+NMAX];

void dfs(int u) {
    for(int node : g[u]) {
        if(visited[node] == 0) {
            visited[node] = 1;
            dfs(node);
        }
    }
    sorted.push_back(u);
}

vector<int> sol[1+NMAX];
void dfsT(int u,int ind) {
    sol[ind].push_back(u);
    for(int node: gT[u]) {
        if(visitedT[node] == 0) {
            visitedT[node] = 1;
            dfsT(node,ind);
        }
    }
}

int main() {
    int n,m;
    cin >> n >> m;
    for(int i = 1; i <= m; i ++) {
        int x,y;
        cin >> x >> y;
        g[x].push_back(y);
        gT[y].push_back(x);
    }
    for(int i = 1;i <= n;i ++) {
        if(visited[i] == 0) {
            visited[i] = 1;
            dfs(i);
        }
    }
    int nsol = 0;
    reverse(sorted.begin(),sorted.end());
    for(int i = 1;i <= n;i ++) {
        if(visitedT[i] == 0) {
            nsol ++;
            visitedT[i] = 1;
            dfsT(i,i);
        }
    }
    cout << nsol << "\n";
    for(int i = 1;i <= n;i ++) {
        if(sol[i].size() > 0) {
            for(int j = 0;j < sol[i].size();j ++)
                cout << sol[i][j] << " ";
            cout << "\n";
        }
    }
    return 0;
}