#include <bits/stdc++.h>

using namespace std;

vector<int> g[100010],gt[100010];
vector<vector<int> > comp;
int q[100010],nr;
char vaz[100010];

void dfs1(int nod)
{
    vaz[nod]=1;
    for(vector<int>::iterator it=g[nod].begin();it!=g[nod].end();it++)
        if(!vaz[*it]) dfs1(*it);
    q[++nr]=nod;
}

void dfs2(int nod,vector<int> &comp)
{
    vaz[nod]=0;
    comp.push_back(nod);
    for(vector<int>::iterator it=gt[nod].begin();it!=gt[nod].end();it++)
        if(vaz[*it]) dfs2(*it,comp);
}

int main()
{
    freopen("ctc.in", "r" ,stdin);
    freopen("ctc.out", "w", stdout);
    int n,m,x,y;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!vaz[i]) dfs1(i);
    for(int i=nr;i;i--)
        if(vaz[q[i]])
        {
            comp.push_back(vector<int>());
            dfs2(q[i],comp.back());
        }
    printf("%d\n",comp.size());
    for(int i=0;i<comp.size();i++)
    {
        for(int j=0;j<comp[i].size();j++) printf("%d ",comp[i][j]);
        printf("\n");
    }
    return 0;
}