#include <fstream>
#include <vector>
#include <bitset>
#include <stack>
#include <algorithm>

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

const int N = 1e5 + 1;
int n, m, nc;
vector <int> a[N], a_t[N], afis[N];
bitset <N> viz;
stack <int> q;

void dfs(int x)
{
    viz[x] = true;
    for(auto y : a[x]){
        if(!viz[y]) dfs(y);
    }
    q.push(x);
}

void dfs_t(int x)
{
    viz[x] = true;
    for(auto y : a_t[x]){
        if(!viz[y])
        {
            afis[nc].push_back(y);
            dfs_t(y);
        }
    }
}

int main()
{
    in >> n >> m;
    for(int i=0; i<m; i++){
        int x, y;
        in >> x >> y;
        a[x].push_back(y);
        a_t[y].push_back(x);
    }

    for(int i=1; i<=n; i++){
        if(!viz[i]) dfs(i);
    }

    for(int i=1; i<=n; i++)
        viz[i] = false;

    while(!q.empty()){
        int i = q.top();
        q.pop();
        if(!viz[i])
        {
            nc++;
            afis[nc].push_back(i);
            dfs_t(i);
        }
    }

    out << nc << "\n";

    for(int i=1; i<=nc; i++)
    {
        sort(afis[i].begin(),afis[i].end());
        for(auto j : afis[i])
            out << j << " ";
        out << "\n";
    }
    return 0;
}