#include <iostream>
#include <vector>
#include <stack>
using namespace std;
//ifstream cin("ctc.in");
//ofstream cout("ctc.out");
vector<int> v[100005],g[100005],sol[100005];
stack<int> s;
int n,m,i,x,y,j,nr,ctc[100005];
bool viz1[100005],viz2[100005];
void dfs(int nod)
{
    viz1[nod]=1;
    for(auto x:v[nod])
    {
        if(viz1[x]==0) dfs(x);
    }
    s.push(nod);
}
void dfs2(int nod)
{
    viz2[nod]=1;
    sol[nr].push_back(nod);
    for(auto x:g[nod])
    {
        if(viz2[x]==0) dfs2(x);
    }
}
int main()
{
    cin>>n>>m;
    for(i=1;i<=m;i++)
    {
        cin>>x>>y;
        v[x].push_back(y);
        g[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    {
        if(!viz1[i])
        {
            dfs(i);
        }
    }
    while(!s.empty())
    {
        int nod=s.top();
        s.pop();
        if(viz2[nod]) continue;
        nr++;
        dfs2(nod);
    }
    cout<<nr<<'\n';
    for(i=1;i<=nr;i++)
    {
        for(auto x:sol[i]) cout<<x<<' ';
        cout<<'\n';
    }
    return 0;
}