#include <iostream>
#include <cstdio>
#include <vector>
#include <stack>
#include <cstring>

#define NMAX 100005
using namespace std;

int N,M;
vector<int> graf[NMAX];
vector<int> graf_transpus[NMAX];
int viz[NMAX];
stack<int> s;

void citire()
{
    scanf("%d%d",&N,&M);
    for(int i=1; i<=M; i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);

        graf[x].push_back(y);
        graf_transpus[y].push_back(x);
    }
}

void dfs1(int c)
{
    viz[c]=1;
    for(vector<int>::iterator ii = graf[c].begin();ii!=graf[c].end();ii++)
        if(!viz[*ii])
            dfs1(*ii);
    s.push(c);
}

int K;
vector<int> rez[NMAX];

void dfs2(int c)
{
    rez[K].push_back(c);
    viz[c]=1;
     for(vector<int>::iterator ii = graf_transpus[c].begin();ii!=graf_transpus[c].end();ii++)
        if(!viz[*ii])
            dfs2(*ii);
    return;

}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    dfs1(1);
    memset(viz,0,sizeof(viz));
    while(!s.empty())
    {
        int c = s.top();
        if(viz[c]==0)
            {
                K++;
                dfs2(c);
            }
        s.pop();
    }
    cout<<K<<endl;
    for(int i=1;i<=K;i++)
    {
        for(vector<int>::iterator ii = rez[i].begin();ii!=rez[i].end();ii++)
        cout<<*ii<<" ";
        cout<<endl;
    }


    return 0;
}