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#include <bits/stdc++.h>
#define NMax 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int N,M,nr;
vector<int> G[NMax],T[NMax],sol[NMax];
bool mark[NMax];
stack<int> Stack;
void Read()
{
fin>>N>>M;
for(int i=1;i<=M;i++)
{
int x,y;
fin>>x>>y;
G[x].push_back(y);
T[y].push_back(x);
}
}
void DFS1(int nod)
{
mark[nod]=true;
for(vector<int>::iterator it=G[nod].begin();it!=G[nod].end();it++)
if(mark[*it]==false)
DFS1(*it);
Stack.push(nod);
}
void DFS2(int nod)
{
sol[nr].push_back(nod);
mark[nod]=true;
for(vector<int>::iterator it=T[nod].begin();it!=T[nod].end();it++)
if(mark[*it]==false)
DFS2(*it);
}
void Write()
{
fout<<nr<<"\n";
for(int i=1;i<=nr;i++)
{
for(vector<int>::iterator it=sol[i].begin();it!=sol[i].end();it++)
fout<<*it<<" ";
fout<<"\n";
}
}
int main()
{
Read();
for(int i=1;i<=N;i++)
if(mark[i]==false)
DFS1(i);
memset(mark,false,sizeof(mark));
while(!Stack.empty())
{
if(mark[Stack.top()]==false)
nr++,DFS2(Stack.top());
Stack.pop();
}
Write();
return 0;
}