#include <bits/stdc++.h>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector<int> gr[100002], gi[100002];
int n, m, i, j, x, y;
bool fr[100002];

stack<int> st;

vector<vector<int>> rasp;

static inline void Dfs1(int nod) {
    fr[nod] = true;
    for(int urm : gr[nod]) {
        if(!fr[urm]) Dfs1(urm);
    }

    st.push(nod);
}

static inline void Dfs2(int nod) {
    fr[nod] = true;
    rasp.back().push_back(nod);
    for(int urm : gi[nod]) {
        if(!fr[urm]) Dfs2(urm);
    }
}

int main() {
    fin >> n >> m;
    for(i = 1; i <= m; i++) {
        fin >> x >> y;
        gr[x].push_back(y);
        gi[y].push_back(x);
    }

    for(i = 1; i <= n; i++) {
        if(!fr[i]) Dfs1(i);
    }

    memset(fr, false, sizeof(fr));

    while(!st.empty()) {
        if(!fr[st.top()]) {
            rasp.push_back({});
            Dfs2(st.top());
        }
        st.pop();
    }

    fout << rasp.size() << "\n";
    for(vector<int>& vCur : rasp) {
        for(int cur : vCur) fout << cur << " ";
        fout << "\n";
    }

    return 0;
}