#include <iostream>
#include <cstdio>
#include <vector>
#include <bitset>

using namespace std;
int n,m;
int a,b;
vector <int> g[100003], gt[100003];
vector <int> s,ts;
vector <vector<int>> sol;
int viz[100003];
void dfs(int ln)
{
    viz[ln]=1;
    for(int i:g[ln])
    {
        if(viz[i]==0)
            dfs(i);
    }
    s.push_back(ln);
}
void dfst(int ln)
{
    viz[ln]=2;
    for(int i:gt[ln])
        if(viz[i]==1)
            dfst(i);
    ts.push_back(ln);
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d %d", &n,&m);
    for(int i=0;i<m;++i)
    {
        scanf("\n%d %d", &a,&b);
        g[a].push_back(b);
        gt[b].push_back(a);
    }
    for(int i=1;i<=n;++i)
    {
        if(viz[i]==0)
        {
            ts.clear();
            s.clear();
            dfs(i);
            dfst(i);
            sol.push_back(ts);
            for(int j:s)
            {
                if(viz[j]==1)
                    viz[j]=0;
            }
        }
    }
    cout<<sol.size()<<"\n";
    for(vector<int> i:sol)
    {
        for(int j:i)
            cout<<j<<" ";
        cout<<"\n";
    }
    return 0;
}