#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pi;
#define pb push_back
#define mp make_pair
#define f first
#define s second

int n, m;
vector<bool> visited(1e5+5);
vector<vi> adj(1e5+5), adj_inv(1e5+5), ans(1e5+5);
stack<int> L;

void dfs(int x){
    visited[x] = 1;
    for(auto i : adj[x]){
        if(!visited[i])
            dfs(i);
    }
    L.push(x);
}

void dfs2(int x, int nr){
    visited[x] = 1;
    ans[nr].pb(x);
    for(auto i : adj_inv[x]){
        if(!visited[i])
            dfs2(i, nr);
    }
}

void solve(){
    cin >> n >> m;
    for(int i = 0; i < m; i++){
        int a, b;
        cin >> a >> b;
        adj[a].pb(b);
        adj_inv[b].pb(a);
    }
    for(int i = 1; i <= n; i++){
        if(!visited[i])
            dfs(i);
    }
    visited = vector<bool>(1e5+5);
    int nr = 1;
    for(int i = 0; i < n; i++){
        int cur = L.top();
        if(!visited[cur]){
            dfs2(cur, nr);
            nr++;
        }
        L.pop();
    }
    cout << nr-1 << '\n';
    for(int i = 1; i < nr; i++){
        for(auto j : ans[i])
            cout << j << ' ';
        cout << '\n';
    }
}
 
int main(){
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    ios::sync_with_stdio(0); cin.tie(0);
    int t = 1;
    //cin >> t;
    while(t--){
        solve();
    }
}