#include <bits/stdc++.h>

using namespace std;
const int N=100010;
ifstream f("ctc.in");
ofstream g("ctc.out");
int n,m,i,x,y,nr,a[N],b[N];
vector<vector<int> > C;
vector<int> v[N],c;
stack<int> St;
bitset<N> ok;
void dfs(int poz);
int main()
{
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
    }
    for(i=1;i<=n;i++)
        if(!a[i])
            dfs(i);
    g<<C.size()<<'\n';
    for(auto it:C)
    {
        for(auto that:it)
            g<<that<<' ';
        g<<'\n';
    }
    return 0;
}
void dfs(int nod)
{
    a[nod]=b[nod]=++nr;
    St.push(nod);ok[nod]=1;
    for(auto it:v[nod])
    {
        if(!a[it])
        {
            dfs(it);
            b[nod]=min(b[nod],b[it]);
        }
        else
            if(ok[it])
                b[nod]=min(b[nod],b[it]);
    }
    if(a[nod]!=b[nod])return ;
    c.resize(0);
    for(;;)
    {
        int x=St.top();
        c.push_back(x);St.pop();ok[x]=0;
        if(x==nod)break;
    }
    C.push_back(c);
    return ;
}