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

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

int n, m, x, y, conex, k, S[nMax];
bool viz[nMax];
vector<int> G[nMax], GT[nMax], cx[nMax];

void dfs(int nod)
{
    viz[nod]=1;
    for(auto i:G[nod])
        if(!viz[i])
            dfs(i);
    S[++k]=nod;
}

void dfsgt(int nod)
{
    viz[nod]=1;
    cx[conex].push_back(nod);
    for(auto i:GT[nod])
        if(!viz[i])
            dfsgt(i);
}

int main()
{
    fin >> n >> m;
    while(m--)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i=1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    for(int i=1; i<=n; i++)
        viz[i]=0;
    for(int i=k; i>=1; i--)
        if(!viz[S[i]])
    {
        conex++;
        dfsgt(S[i]);
    }
    fout << conex << "\n";
    for(int i=1; i<=conex; i++)
    {
        sort(cx[i].begin(), cx[i].end());
        for(auto j:cx[i])
            fout << j << " ";
        fout << "\n";
    }
    return 0;
}