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

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

vector<int> compcon[100009];
vector<int> v[100009];
vector<int> t[100009];
int viz[100009],nr;
stack<int>s;

void dfs(int n)
{
    viz[n] = 1;
    for(int i=0; i<v[n].size(); i++)
    {
        if(viz[v[n][i]]==0)
            dfs(v[n][i]);
    }
s.push(n);

}


void dfs_t(int n)
{
    compcon[nr].push_back(n);

    viz[n] = 2;

    for(int i=0; i<t[n].size(); i++)
    {
        if(viz[t[n][i]] == 1)
            dfs_t(t[n][i]);
    }
}

int main()
{
    int m,n,x,y;
    f>>n>>m;
    for(int i =1; i <=m ; i++)
    {
        f>>x>>y;
t[y].push_back(x);
        v[x].push_back(y);

    }



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



    while(s.empty()==0)
    {
        int n=s.top();
        if(viz[n]==1)
        {
            nr++;
            dfs_t(n);
        }
        s.pop();
    }
    g<<nr<<"\n";


    for(int i = 1; i <= nr; i++)
    {
        for(int j=0; j<compcon[i].size(); j++)
        {
            g<<compcon[i][j]<<" ";
        }

        g<<"\n";
    }
}