#include <bits/stdc++.h>
using namespace std;
int n, m, viz[100005], x, y, nrctc, w[1005], nr;
vector<int> v[100005], vtr[100005], comp[100005];
stack <int> s;
ifstream f("ctc.in");
ofstream g("ctc.out");
void dfs(int k)
{
    viz[k] = 1;
    for(int i = 0; i < v[k].size(); i ++)
      if(!viz[v[k][i]]) dfs(v[k][i]);
    s.push(k);
    w[++ nr] = k;
}
void dfstr(int k)
{
    viz[k] = 2;
    comp[nrctc].push_back(k);
    for(int i = 0; i < vtr[k].size(); i ++)
      if(viz[vtr[k][i]] == 1) dfstr(vtr[k][i]);
}
int main()
{
    f >> n >> m;
    while(m --)
    {
        f >> x >> y;
        v[x].push_back(y);
        vtr[y].push_back(x);
    }
    for(int i = 1; i <= n; i ++)
      if(!viz[i]) dfs(i);
    while(!s.empty())
    {
        int nod = s.top();
        if(viz[nod] == 1)
        {
            nrctc++;
            dfstr(nod);
        }
        s.pop();
    }
    g << nrctc << "\n";
    for(int i = 1; i <= nrctc; i ++)
    {
        for(int j = 0; j < comp[i].size(); j ++)
          g << comp[i][j] << " ";
        g << "\n";
    }
    return 0;
}