#include <bits/stdc++.h>
#define NMAX 100001

using namespace std;

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

vector<int> a[NMAX], a_t[NMAX];
vector<int> ctc[NMAX];
bitset<NMAX> viz;
stack<int> stiva;
int cnt;

void dfs(int k) {
    viz[k] = 1;
    for(auto x : a[k])
        if(!viz[x])
            dfs(x);
    stiva.push(k);
}

void dfs_t(int k) {
    viz[k] = 1;
    ctc[cnt].push_back(k);
    for(auto x: a_t[k])
        if(!viz[x])
            dfs_t(x);
}

int main() {
    int n, m;
    fin >> n >> m;
    for (int i = 0; i < m; i++) {
        int x, y;
        fin >> x >> y;
        a[x].push_back(y);
        a_t[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if (!viz[i])
            dfs(i);

    viz.reset();
    while(!stiva.empty()) {
        int x = stiva.top();
        stiva.pop();
        if(!viz[x])
        {
            cnt++;
            dfs_t(x);
        }
    }
    fout << cnt << '\n';
    for(int i = 1; i <= cnt; i++) {
        for(auto x : ctc[i])
            fout << x << ' ';
        fout << '\n';
    }
}