#include <bits/stdc++.h>

using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int numar,n,m,viz[100005],x,y,nr[100005],q,i,j;
vector <int> sol[100005],v[100005],inv[100005];
void dfs(int x)
{
    int i;
    viz[x]=1;
    for (i=0;i<v[x].size();i++)
    {
        if (viz[v[x][i]]==0)
        {
            dfs(v[x][i]);
        }
    }
    nr[++q]=x;
}
void dfs2(int x)
{
    int i;
    viz[x]=1;
    sol[numar].push_back(x);
    for (i=0;i<inv[x].size();i++)
    {
        if (viz[inv[x][i]]==0)
        {
            dfs2(inv[x][i]);
        }
    }
}
int main()
{
    f>>n>>m;
    for (i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        inv[y].push_back(x);
    }
    for (i=1;i<=n;i++)
    {
        if (viz[i]==0)
        {
            dfs(i);
        }
    }
    memset(viz,0,sizeof(viz));
    for (i=q;i>=1;i--)
    {
        if (viz[nr[i]]==0)
        {
            numar++;
            dfs2(nr[i]);
        }
    }
    g<<numar<<'\n';
    for (i=1;i<=numar;i++)
    {
        sort (sol[i].begin(),sol[i].end());
        for (j=0;j<sol[i].size();j++)
        {
            g<<sol[i][j]<<" ";
        }
        g<<'\n';
    }
    return 0;
}