#include <bits/stdc++.h>
using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
const int lim=1e5+4;
vector<int> vec[lim];
vector<int> rev[lim];
stack<int> st;
bool ok[lim];
int n,m,x,y;
void df(int nod)
{
    ok[nod]=true;
    for(int x:vec[nod])
    if(!ok[x]) df(x);
    st.push(nod);
}
int cnt;
vector<int> grupa[lim];
void df2(int nod)
{
    ok[nod]=true;
    grupa[cnt].push_back(nod);
    for(int x:rev[nod])
    if(!ok[x]) df2(x);
}
int main()
{
    ios_base::sync_with_stdio(false);
    in.tie(0),out.tie(0);
    in>>n>>m;
    for(int i=1;i<=m;++i)
        in>>x>>y,
        vec[x].push_back(y),
        rev[y].push_back(x);
    for(int i=1;i<=n;++i)
    if(!ok[i]) df(i);
    memset(ok,0,sizeof(ok));
    while(!st.empty())
    {
        int nod=st.top(); st.pop();
        if(ok[nod]) continue;
        ++cnt;
        df2(nod);
    }
    out<<cnt<<'\n';
    for(int i=1;i<=cnt;++i)
    {
        for(int x:grupa[i])
            out<<x<<' ';
        out<<'\n';
    }
    return 0;
}