#include <bits/stdc++.h>
#define endl "\n"
using namespace std;

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

#define cin  fin
#define cout fout

#define Nmax 100010

int n, contor;

vector < int > g1[Nmax], g2[Nmax], sol[Nmax];
stack < int > stiva;

bitset < Nmax > viz1;
bitset < Nmax > viz2;

void read() {
    int m;
    cin >> n >> m;
    while(m--)
    {
        int x, y;
        cin >> x >> y;
        g1[x].push_back(y);
        g2[y].push_back(x);
    }
}

void DFS(int nod) {
    viz1[nod] = 1;

    for(const auto it : g1[nod]) {
        if(viz1[it] == 0) {
            DFS(it);
            stiva.push(it);
        }
    }
}

void dfs(int nod) {
    sol[contor].push_back(nod);
    viz2[nod] = 1;

    for(const auto it : g2[nod]) {
        if(viz2[it] == 0) {
            dfs(it);
        }
    }
}


void solve() {
    DFS(1);

    while(!stiva.empty()) {
        int nod = stiva.top();
        stiva.pop();

        if(viz2[nod] == 0) {
            contor++;
            dfs(nod);
        }
    }
}

void afis() {
    cout << contor << endl;
    for(int i=1; i<=contor; i++)
    {
        for(const auto it : sol[i]) {
            cout << it << " ";
        }
        cout << endl;
    }
}

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