#include <bits/stdc++.h>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int NMAX=100005;

int N, M, comp;
vector<int> g1[NMAX], g2[NMAX], sol[NMAX];
bool viz1[NMAX], viz2[NMAX];
stack<int> st;

void dfs1(int nod){
    viz1[nod]=true;
    for(auto x: g1[nod]){
        if(viz1[x]==false)
            dfs1(x);
    }
    st.push(nod);
}

void dfs2(int nod){
    sol[comp].push_back(nod);
    viz2[nod]=true;
    for(auto x: g2[nod]){
        if(viz2[x]==false)
            dfs2(x);
    }
}

int main()
{
    fin>>N>>M;
    int x, y;
    for(int i=1;i<=M;i++){
        fin>>x>>y;
        g1[x].push_back(y);
        g2[y].push_back(x);
    }

    for(int i=1;i<=N;i++)
        if(viz1[i]==false)
            dfs1(i);

    while(!st.empty()){
        if(viz2[st.top()]==false){
            comp++;
            dfs2(st.top());
        }
        st.pop();
    }

    fout<<comp<<'\n';
    for(int i=1;i<=comp;i++){
        for(auto x: sol[i])
            fout<<x<<' ';
        fout<<'\n';
    }

    fin.close();
    fout.close();
    return 0;
}