#include <bits/stdc++.h>

using namespace std;
const int N = 1e5 + 5;
vector <int> g[N];
int id[N], low[N], st[N], k, timer;
bool inst[N];
vector <vector <int>> ctc;
void dfs(int u)
{
    inst[u] = low[u] = id[u] = ++timer;
    st[k++] = u;
    for(int v : g[u]) {
        if(!id[v]) {
            dfs(v);
            low[u] = min(low[u], low[v]);
        } else if(inst[v]) low[u] = min(low[u], id[v]);
    }
    if(low[u] == id[u]) {
        ctc.push_back({u});
        while(st[--k] != u) {
            ctc.back().push_back(st[k]);
            inst[st[k]] = false;
        }
        inst[u] = false;
    }
}

int main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    int n, m;
    cin >> n >> m;
    for(int i = 0, u, v; i < m; i++)
        cin >> u >> v,
        g[u].push_back(v);
    for(int i = 1; i <= n; i++) if(!id[i])
        dfs(i);
    cout << ctc.size() << "\n";
    for(auto& comp : ctc) {
        for(int x : comp)
            cout << x << " ";
        cout << "\n";
    }
    return 0;
}