using namespace std;
#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100003
ifstream in("ctc.in");
ofstream out("ctc.out");
int N,M;
vector <int> graph[NMAX],tgraph[NMAX],comp;
vector < vector<int> > sol;
stack <int> S;
int viz1[NMAX],viz2[NMAX];//,all_visited=false,removed[NMAX];
void dfs(int node)
{
    vector<int>::iterator it;
    viz1[node]=1;
    for (it=graph[node].begin();it!=graph[node].end();it++)
        if (viz1[*it]==0) dfs(*it);
    S.push(node);

}
void dfst(int node)
{
    vector<int>::iterator it;
    comp.push_back(node);
    viz2[node]=1;
    for (it=tgraph[node].begin();it!=tgraph[node].end();it++)
        {   if (viz2[*it]==0)
            dfst(*it);
        }

}
int main()
{

    int x,y,i;
    in>>N>>M;
    for (i=1;i<=N;i++) {viz1[i]=viz2[i]=0;}
    for (i=1;i<=M;i++)
        {
            in>>x>>y;
            graph[x].push_back(y);
            tgraph[y].push_back(x);
        }

    for (i=1;i<=N;i++)
     if (viz1[i]==0) dfs(i);

    while (!S.empty())
    {
        x=S.top();S.pop();
        if (viz2[x]==0)
        {
            dfst(x);
            sol.push_back(comp);
            comp.clear();
        }
    }
    vector<int>::iterator it;
    out<<sol.size()<<"\n";
    for(i=0;i<sol.size();i++)
    {
        for(it=sol[i].begin();it!=sol[i].end();it++)
            out<<*it<<" ";
        out<<"\n";
    }
    return 0;
}