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

using namespace std;

const int NT=100000+7;
int n,m;
vector <int> g1[NT];
vector <int> g2[NT];
int ord[NT],top;
bool jeg[NT];

void ju(int nod)
{
        jeg[nod]=1;
        for(auto &nou : g1[nod])
                if(jeg[nou]==0)
                        ju(nou);
        ord[++top]=nod;
}

vector <int> uc;
void jo(int nod)
{
        jeg[nod]=1;
        uc.push_back(nod);
        for(auto &bou : g2[nod])
                if(jeg[bou]==0)
                        jo(bou);
}

int main()
{
        freopen("ctc.in","r",stdin),
        freopen("ctc.out","w",stdout);

        scanf("%d%d",&n,&m);
        for(int i=1;i<=m;i++)
        {
                int a,b;
                scanf("%d%d",&a,&b);
                g1[a].push_back(b);
                g2[b].push_back(a);
        }

        vector <vector <int>> luv;

        for(int i=1;i<=n;i++)
                if(jeg[i]==0)
                        ju(i);
        for(int i=1;i<=n;i++)
                jeg[i]=0;
        for(int i=n;i>=1;i--)
                if(jeg[ord[i]]==0)
                {
                        uc.clear();
                        jo(ord[i]);
                        luv.push_back(uc);
                }
        cout<<(int)luv.size()<<"\n";
        for(auto &x : luv)
        {
                for(auto &y : x)
                        cout<<y<<" ";
                cout<<"\n";
        }

        return 0;
}