#include <bits/stdc++.h>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector<int>v[100010],vt[100010],ctc[100010];
stack<int>s;
int n,m,x,y,i,viz[100010],cnt,nod;
void dfs(int nod)
{
    viz[nod]=1;
    for(auto it:v[nod])
        if(!viz[it])
            dfs(it);
    s.push(nod);
}
void dfsT(int nod)
{
    viz[nod]=1;
    ctc[cnt].push_back(nod);
    for(auto it:vt[nod])
        if(!viz[it])
            dfsT(it);
}
int main()
{
    fin>>n>>m;
    while(m--)
    {
        fin>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(!viz[i])
            dfs(i);
    memset(viz,0,sizeof(viz));
    while(!s.empty())
    {
        nod=s.top();
        s.pop();
        if(viz[nod])
            continue;
        cnt++;
        dfsT(nod);
    }
    fout<<cnt<<'\n';
    for(i=1;i<=cnt;i++)
    {
        for(auto j:ctc[i])
            fout<<j<<" ";
        fout<<'\n';
    }
    return 0;
}