#include <bits/stdc++.h>

using namespace std;

const int DIM = 1e5;

vector <int> l[DIM];
vector <int> lt[DIM];

int viz[DIM];

stack <int> s;

vector <int> cc[DIM];

void dfs(int x)
{
    viz[x] = 1;

    for(int i = 0; i < l[x].size(); i++)
    {
        int vec = l[x][i];

        if(viz[vec] == 0)
            dfs(vec);
    }

    s.push(x);

}

void dfst(int x,int cnt)
{
    viz[x] = 2;
    cc[cnt].push_back(x);

    for(int i = 0; i < lt[x].size(); i++)
    {
        int vec = lt[x][i];

        if(viz[vec] == 1)
        {
            dfst(vec,cnt);
        }

    }

}

int main()
{
    int n, m;
    in >> n >> m;

    for(int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;

        l[x].push_back(y);
        lt[y].push_back(x);
    }

    for(int i = 1; i <= n; i++)
        if(viz[i] == 0)
        {
            dfs(i);
        }

       int cnt = 0;

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

        if(viz[nod] == 1)
        {
            cnt++;
            dfst(nod,cnt);
        }
    }
    out << cnt <<'\n';

    for(int i = 1; i <= cnt; i++)
        {
          for(int j = 0; j < cc[i].size(); j++)
            out << cc[i][j] <<" ";

            out <<'\n';
        }
    return 0;
}