#include <cstdio>
#include <cstring>

#include <stack>
#include <vector>

using namespace std;

const int MAXN = 100001;

vector<int> G[MAXN];
vector<int> GT[MAXN];

stack<int> st;
vector<int> sol;
vector<vector<int> > sols;

bool dead[MAXN];
bool vis[MAXN];
bool vis_trans[MAXN];

void dfs(int node)
{
    vis[node] = true;
    vector<int>::iterator it;
    for (it = G[node].begin(); it != G[node].end(); ++it) {
        if (dead[*it] || vis[*it])
            continue;
        dfs(*it);
    }
    st.push(node);
}

void dfs_trans(int node)
{
    sol.push_back(node);
    vis_trans[node] = true;
    dead[node] = true;
    vector<int>::iterator it;
    for (it = GT[node].begin(); it != GT[node].end(); ++it) {
        if (dead[*it] || vis_trans[*it])
            continue;
        dfs_trans(*it);
    }
}

void components()
{
    while (!st.empty()) {
        int node = st.top();
        st.pop();
        if (dead[node])
            continue;
        sol.clear();
        dfs_trans(node);
        sols.push_back(sol);
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);

    int n, m;
    scanf("%d %d", &n, &m);
    for (int i = 0; i < m; ++i) {
        int x, y;
        scanf("%d %d", &x, &y);
        G[x].push_back(y);
        GT[y].push_back(x);
    }

    memset(dead, false, sizeof(dead));
    memset(vis, false, sizeof(vis));
    memset(vis_trans, false, sizeof(vis_trans));
    for (int i = 1; i <= n; ++i) {
        if (!dead[i] && !vis[i]) {
            dfs(i);
            components();
        }
    }

    printf("%lu\n", sols.size());
    for (int i = 0; i < sols.size(); ++i) {
        vector<int>::iterator it;
        for (it = sols[i].begin(); it != sols[i].end(); ++it)
            printf("%d ", *it);
        printf("\n");
    }

    return 0;
}