#include <bits/stdc++.h>
#define NMAX 100001
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m,used[NMAX];
vector< int > v[NMAX],g[NMAX],sol[NMAX];
deque< int > q;
int tare;
void dfs1( int k)
{
    used[k]=1;
    for( auto x :v[k])
        if(!used[x])
        dfs1(x);
    q.push_back(k);
}
void dfs( int k)
{
    sol[tare].push_back(k);
    used[k]=1;
    for(auto x: g[k])
        if(!used[x])dfs(x);
}
int main()
{
    fin>>n>>m;
    while(m)
    {
        int x, y;
        fin>>x>>y;
        v[x].push_back(y);
        g[y].push_back(x);
        --m;
    }
    for(int i=1;i<=n;++i)
        if(!used[i])dfs1(i);
    memset(used, 0, sizeof(used));

    while(q.size())
    {
        int t=q.back();
        q.pop_back();
        if(!used[t])
        {
            ++tare;
            dfs(t);
        }
    }
    fout<<tare<<"\n";
    for(int i=1;i<=tare;++i,fout<<"\n")
        for(int j=0;j<sol[i].size();++j)fout<<sol[i][j]<<" ";
    return 0;
}