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

#define NMAX 100005
#define MMAX 200005

using namespace std;

int N,M;
vector<int> graf[NMAX];
vector<int> graft[NMAX];

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);
        graft[y].push_back(x);
    }

}

stack<int> s;
int viz[NMAX];

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

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

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

void rezolvare()
{
    for(int i=1;i<=N;i++)
        if(!viz[i])
            dfs1(i);
    memset(viz,0,sizeof(viz));
    while(!s.empty())
    {
        if(!viz[s.top()])
        {
            K++;
            dfs2(s.top());
        }
        s.pop();
    }
}

void afisare()
{
    printf("%d\n",K);
    for(int i=1;i<=K;i++)
    {
        for(vector<int>::iterator ii = rez[i].begin();ii!=rez[i].end();ii++)
            printf("%d ",*ii);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    rezolvare();
    afisare();
    return 0;
}