/*
    Those without power, seek us!
    Those with power, fear us!
    We are the Order of the Black Knights!
*/

#include<fstream>
#include<cstdio>
#include<map>
#include<set>
#define FIT(a,b) for(vector<int >::iterator a=b.begin();a!=b.end();a++)
#define FITP(a,b) for(vector<pair<int,int> >::iterator a=b.begin();a!=b.end();a++)
#define RIT(a,b) for(vector<int>::reverse_iterator a=b.end();a!=b.begin();++a)
#include<stack>
#define ROF(a,b,c) for(int a=b;a>=c;--a)
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#define REP(a,b) for(register int a=0;a<b;++a)
#include<cstring>
#include<ctime>
#include<bitset>
#include<cmath>
#include<iomanip>
#include<set>
#define f cin
#define g cout
#include<queue>
#define debug cerr<<"OK";
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ll long long
#define ull unsigned int
#define mod 1000000009LL
#define SQR 350
#define inf 1<<30
#define div fdasfasd
#define hash dsafdsfds
#define od 100003
#define mod  1999999973LL
#define DIM 60010000
#define base 256
#define bas 255
#define N 100100
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
/*
    int dx[]={0,0,0,1,-1};
    int dy[]={0,1,-1,0,0};
*/
stack<int> st;
vector<int> v[N],u[N],C[N];
int ctc,viz[N],n,m,x,y,k;
void dfs(int x)
{
    viz[x]=k;
    FIT(it,v[x])
    if(!viz[*it])
        dfs(*it);
    st.push(x);
}
void dfs1(int x)
{
    C[ctc].pb(x);
    viz[x]=0;
    FIT(it,u[x])
    if(viz[*it]==k)
        dfs1(*it);
}
int main ()
{
    f>>n>>m;
    FOR(i,1,m)
    {
        f>>x>>y;
        v[x].pb(y);
        u[y].pb(x);
    }
    FOR(i,1,n)
    if(!viz[i])
    {
        ++k;
        dfs(i);
    }
    while(1)
    {
        while(!st.empty()&&!viz[st.top()])
            st.pop();
        if(st.empty())
            break;
        int x=st.top();
        k=viz[x];
        st.pop();
        ++ctc;
        dfs1(x);
    }
    g<<ctc<<"\n";
    FOR(i,1,ctc)
    {
        FIT(it,C[i])
            g<<*it<<" ";
        g<<"\n";
    }
    return 0;
}