#include <bits/stdc++.h>
using namespace std;
vector<int>g[100003];
vector<int>gr[100003];
int n,m;
stack<int>s;
vector<vector<int> >sol;
vector<int>curr;
bool vis[100003];
bool vis2[100003];
void dfs(int node){
vis[node]=true;
for(int j=0;j<g[node].size();j++)
if(!vis[g[node][j]])
dfs(g[node][j]);
s.push(node);
}
void dfs2(int node){
curr.push_back(node);
vis2[node]=true;
for(int j=0;j<gr[node].size();j++)
if(!vis2[gr[node][j]])
dfs2(gr[node][j]);

}
void kosaraju(){
for(int j=1;j<=n;j++)
if(!vis[j])
dfs(j);

while(!s.empty()){
int k=s.top();
s.pop();
if(!vis2[k])
dfs2(k);
if(curr.size()!=0)
sol.push_back(curr);
curr.clear();

}
}
int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin>>n>>m;
    for(int i=0;i<m;i++){
    int a,b;
    cin>>a>>b;
    g[a].push_back(b);
    gr[b].push_back(a);
    }
    kosaraju();
    cout<<sol.size()<<"\n";
    for(int i=0;i<sol.size();i++)
    {

        for(int j=0;j<sol[i].size();j++)
        cout<<sol[i][j]<<" ";
        cout<<"\n";
    }
    return 0;
}