#include<iostream>
#include<vector>
#include<deque>
#include<queue>
#include<stack>
#include<set>
#include<unordered_map>
#include<map>
#include<unordered_set>
#include<ctime>
#include<random>
#include<algorithm>
#include<cstring>
#include<cmath>
#define fi first
#define se second
#define eb emplace_back
#define pb push_back
using namespace std;
using pii = pair<int,int>;
using ll = long long;
using ld = long double;

mt19937 rng(time(nullptr));

constexpr int NMAX = 1e5 + 1;

vector<int> g[2][NMAX]; bool viz[NMAX];

void dfs(int a,int id,vector<int> &v)
{
    viz[a] = 1;
    for(auto &it : g[id][a])
        if(!viz[it]) dfs(it,id,v);
    v.eb(a);
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);

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

    int n,m,a,b; cin >> n >> m;
    for(int i = 0 ; i < m ; i++)
        {
            cin >> a >> b;
            g[0][a].eb(b);
            g[1][b].eb(a);
        }

    vector<vector<int>> comps; vector<int> o;
    for(int i = 1; i <= n ; i++)
        if(!viz[i]) dfs(i,0,o);
    reverse(o.begin(),o.end()); memset(viz,0,sizeof(viz));
    for(auto &v : o)
        {
            if(viz[v]) continue;
            vector<int> comp; dfs(v,1,comp);
            comps.pb(comp);
        }

    cout << comps.size() << '\n';
    for(int i = 0 ; i < comps.size() ; i++, cout << '\n')
        for(auto &it : comps[i])
            cout << it << " ";
}