#include <iostream>
#include <fstream>
#include <stack>
#include <vector>
#define infinit (1<<28)

using namespace std;

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

int v, e;
int x, y;
vector<int> graf[100005], complement[100005], sol[100005];
stack<int> s;
bool viz[100005];
int comp;

void dfs(int vf)
{
    viz[vf] = 1;
    for(auto& vec:graf[vf])
    {
        if(viz[vec] == 0)
            dfs(vec);
    }
    s.push(vf);
}

void dfsc(int vf)
{
    viz[vf] = 0;
    sol[comp].push_back(vf);
    for(auto& vec:complement[vf])
    {
        if(viz[vec] == 1)
            dfsc(vec);
    }
}

void kosaraju()
{
    for(int i=1; i<=v; i++)
    {
        if(viz[i] == 0)
            dfs(i);
    }
    while(!s.empty())
    {
        int vf=s.top();
        s.pop();
        if(viz[vf] == 1)
        {
            dfsc(vf);
            comp++;
        }
    }
    g<<comp<<'\n';
    for(int i=0; i<comp; i++)
    {
        for(auto& el:sol[i])
            g<<el<<' ';
        g<<'\n';
    }
}


int main() {

    f>>v>>e;

    for(int i=1; i<=e; i++)
    {
        f>>x>>y;
        graf[x].push_back(y);
        complement[y].push_back(x);
    }
    kosaraju();
    return 0;
}