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#include <fstream>
#include<list>
#include<stack>
#include<iostream>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
list<int>v[100002];
list<int>comp[100002];
stack<int> s;
int index=1;
int idx[100003],lowlink[100003],n,m,nrcomp;
bool pe_stiva[100003];
void afis()
{
for(int j=1;j<=n;j++) cout<<idx[j]<<' ';
cout<<"INDEX"<<'\n';
for(int j=1;j<=n;j++) cout<<lowlink[j]<<' ';
cout<<"LINK"<<'\n';
for(int j=1;j<=n;j++) cout<<pe_stiva[j]<<' ';
cout<<"STIVA"<<'\n';
cout<<'\n';
int aux;
cin>>aux;
}
void tarjan(int k)
{ int u;
list<int>:: iterator it;
idx[k]=index;
lowlink[k]=index;
index++;
s.push(k); pe_stiva[k]=1;
// cout<<"k="<<k<<'\n';
//afis();
for(it=v[k].begin();it!=v[k].end();++it)
{
u=*it;
if(idx[u]==0)
{
tarjan(u);
lowlink[k]=min(lowlink[k],lowlink[u]);
}
else if(pe_stiva[u])
{
lowlink[k]=min(lowlink[k],idx[u]);
}
//afis();
}
if(lowlink[k]==idx[k])
{
nrcomp++;
u=s.top();
do {
u=s.top();
comp[nrcomp].push_back(u);
s.pop();
pe_stiva[u]=0;
}while(u!=k);
}
}
int main()
{
int i,j,x,y;
f>>n>>m;
for(i=1;i<=m;i++)
{
f>>x>>y;
v[x].push_back(y);
}
for(i=1;i<=n;i++)
if(idx[i]==0) tarjan(i);
g<<nrcomp<<'\n';
list<int>::iterator itf;
for(i=1;i<=nrcomp;i++)
{
for(itf=comp[i].begin();itf!=comp[i].end();++itf)
g<<*itf<<' ';
g<<'\n';
}
f.close();
g.close();
return 0;
}