#include <bits/stdc++.h>
#define N 100001
#define pb push_back
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m, i, j, viz[N], k, x, y;
vector<int> v[N], comp[N], v2[N];
stack<int> stk;
void dfs(int nod)
{
    viz[nod]=1;
    for(auto i:v[nod])
        if(!viz[i])
            dfs(i);
    stk.push(nod);
}
void dfs2(int nod)
{
    viz[nod]=1;
    comp[k].pb(nod);
    for(auto i:v2[nod])
        if(!viz[i])
            dfs2(i);
}
int main()
{
    fin>>n>>m;
    for(i=1;i<=m;++i)
    {
        fin>>x>>y;
        v[x].pb(y);
    }
    for(i=1;i<=n;++i)
        if(!viz[i])
        dfs(i);
    for(i=1;i<=n;++i)
        for(auto j:v[i])
            v2[j].pb(i);
    for(i=1;i<=n;++i)
        viz[i]=0;
    while(!stk.empty())
    {
        int tp=stk.top();
        stk.pop();
        if(viz[tp])
            continue;
        ++k;
        dfs2(tp);
    }
    fout<<k<<'\n';
    for(i=1;i<=k;++i,fout<<'\n')
        for(auto j:comp[i])
            fout<<j<<' ';
    return 0;
}