#include <cstdio>
#include <vector>
#include <stack>
#include <bitset>

using namespace std;

const int nmx = 100002;

int n,m;

vector <int> g[nmx], gt[nmx],aux;
vector <vector<int> > r;
bitset <nmx> viz;
stack <int> st;

void citire()
{
    scanf("%d %d", &n, &m);
    for(int i = 1; i <= m; ++i)
    {
        int nod1,nod2;
        scanf("%d %d", &nod1, &nod2);
        g[nod1].push_back(nod2);
        gt[nod2].push_back(nod1);
    }
}

void dfs(int nod)
{
    viz[nod] = true;
    for(vector<int>::iterator it = g[nod].begin(); it != g[nod].end(); ++it)
        if(viz[*it] == false)
            dfs(*it);
    st.push(nod);
}

void dfs_transpus(int nod)
{
    viz[nod] = true;
    aux.push_back(nod);

    for(vector<int>::iterator it = gt[nod].begin(); it != gt[nod].end(); ++it)
        if(viz[*it] == false)
            dfs_transpus(*it);
}

void plus_minus()
{
    for(int i = 1; i <= n; ++i)
        if(viz[i] == false)
            dfs(i);
    viz.reset();
    while(not st.empty())
    {
        int nod = st.top();
        st.pop();
        if(viz[nod])
            continue;
        aux.clear();
        dfs_transpus(nod);
        r.push_back(aux);
    }
}

void afish()
{
    printf("%d\n", r.size());
    for(size_t i = 0; i < r.size(); ++i)
    {
        for(size_t j = 0; j < r[i].size(); ++j)
            printf("%d ", r[i][j]);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    citire();
    plus_minus();
    afish();
    return 0;
}