#include <fstream>
#include <vector>
#include <stack>

using namespace std;

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

const int NMAX = 100005;

vector <int> g[NMAX], gt[NMAX], comp[NMAX];
stack <int> st;

int viz[NMAX], viz2[NMAX];
int cc;

void dfs1(int nod){
    viz[nod] = 1;
    for(auto i: g[nod]){
        if(!viz[i]){
            dfs1(i);
        }
    }
    st.push(nod);
}

void dfs2(int nod){
    viz2[nod] = cc;
    comp[cc].push_back(nod);
    for(auto i: gt[nod]){
        if(!viz2[i]){
            dfs2(i);
        }
    }
}

void solve(){
    int n, m;
    fin >> n >> m;
    for(int i = 1; i <= m; ++i){
        int x, y;
        fin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(int i = 1; i <= n; ++i){
        if(!viz[i]){
            dfs1(i);
        }
    }
    while(!st.empty()){
        int t = st.top();
        st.pop();
        if(!viz2[t]){
            cc ++;
            dfs2(t);
        }
    }
    fout << cc << "\n";
    for(int i = 1; i <= cc; ++i){
        for(int j = 0; j < comp[i].size(); ++j){
            fout << comp[i][j] << " ";
        }
        fout << "\n";
    }

}

int main()
{
    solve();
    return 0;
}