#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define lsb(x) (x & (-x))
 
using namespace std;
 
const int MAXN = (int) 1e5;
 
vector <int> g[MAXN + 1], gr[MAXN + 1];
bool vis[MAXN + 1];
vector <int> top;
 
void dfs(int nod) {
    vis[nod] = 1;
    for(auto it : g[nod]) {
        if(vis[it] == 0) {
            dfs(it);
        }
    }
    top.push_back(nod);
}
 
vector <vector <int>> sol;
 
void dfs1(int nod) {
    sol.back().push_back(nod);
    vis[nod] = 1;
    for(auto it : g[nod]) {
        if(vis[it] == 0) {
            dfs1(it);
        }
    }
}
 
int main() {
#ifdef HOME
    ifstream cin("A.in");
    ofstream cout("A.out");
#endif
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    int i, n, m;
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    
    cin >> n >> m;
    for(i = 1; i <= m; i++) {
        int x, y; cin >> x >> y;
        g[x].push_back(y);
    }

    
    for(i = 1; i <= n; i++) {
        if(vis[i] == 0) {
            dfs(i);
        }
    }
    reverse(top.begin(), top.end());
    memset(vis, 0, sizeof(vis));
    while(top.size()) {
        if(vis[top.back()] == 0) {
            sol.push_back(vector <int>());
            dfs1(top.back());
        }
        top.pop_back();
    }
    
    cout << sol.size() << "\n";
    for(auto &it : sol) {
        for(auto nod : it) {
            cout << nod << " ";
        }
        cout << "\n";
    }
    
    return 0;
}