#include <bits/stdc++.h>
#define NMAX 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m, cnt, cnt2, tmp[NMAX];
bool vis[NMAX], visrev[NMAX];
vector<int>a[NMAX],b[NMAX],res[NMAX];
 
void kos(int x)
{
    int y;
    vis[x]=true;
    for(int i=0;i<a[x].size();i++)
    {
        y=a[x][i];
        if(!vis[y])
            kos(y);
    }
    tmp[++cnt]=x;
}
void dfsrev(int x)
{
    int y;
    visrev[x]=true;
    res[cnt2].push_back(x);
    for(int i=0;i<b[x].size();i++)
    {
        y=b[x][i];
        if(!visrev[y])
            dfsrev(y);
    }
}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x, y;
        fin>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!vis[i])
            kos(i);
    for(int i=1;i<=n;i++)
        if(!visrev[tmp[i]])
        {
            cnt2++;
            dfsrev(tmp[i]);
        }
    fout<<cnt2<<'\n';
    for(int i=1;i<=cnt2;i++)
    {
        for(int j=0;j<res[i].size();j++)
            fout<<res[i][j]<<' ';
        fout<<'\n';
    }
    return 0;
}