#include <bits/stdc++.h>
#define for0(i, n) for(int i = 0; i < n; i++)
#define for1(i, n) for(int i = 1; i <= n; i++)
#define pb push_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define V vector<int>
#define VP vector<pair<int, int> >
#define FASTIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
using namespace std;
#ifdef _WIN32
#include <windows.h>
#define print(x) PRINT(x, #x)
template<typename T> inline const void PRINT(T VARIABLE, string NAME)
{
#ifndef ONLINE_JUDGE /// ONLINE_JUDGE IS DEFINED ON CODEFORCES
    HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
    SetConsoleTextAttribute(hConsole, 10);
    cerr << NAME << " = " << VARIABLE;
    SetConsoleTextAttribute(hConsole, 7);
    cerr << '\n';
#endif
}
#else
#define print(x) 0
#endif
typedef long long ll;
typedef unsigned long long ull;
const ll INFLL = 2 * (ll)1e18 + 100;
const int INFINT = 2 * (int)1e9 + 100;
const double PI = atan(1) * 4;
const double EPS = 1e-12;
const int SEED = 1e3 + 7;

const int MOD = 1e9 + 7; /// careful here (7 or 9, 66.. etc)
const int NMAX = 1e5 + 5;

ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define cin fin
#define cout fout

int n, m;
V graf[NMAX], graf_inv[NMAX];
bool trecut[NMAX], trecut_inv[NMAX];
V st;

void dfs(int nod)
{
    trecut[nod] = 1;
    for(auto i: graf[nod]) if(!trecut[i]) dfs(i);
    st.pb(nod);
}
vector<vector<int> > SOL;
V sol;
void dfs_inv(int nod)
{
    trecut_inv[nod] = 1;
    sol.pb(nod);
    for(auto i: graf_inv[nod]) if(!trecut_inv[i]) dfs_inv(i);
}

int main()
{
    FASTIO;
    cin >> n >> m;
    for1(i, m)
    {
        int a, b;
        cin >> a >> b;
        graf[a].pb(b);
        graf_inv[b].pb(a);
    }
    for1(i, n) if(!trecut[i]) dfs(i);

    for(int i = n - 1; i >= 0; i--) if(!trecut_inv[st[i]])
    {
        dfs_inv(st[i]);
        SOL.pb(sol);
        sol.clear();
    }
    cout << SOL.size() << '\n';
    for(auto s: SOL)
    {
        for(auto i: s) cout << i << ' ';
        cout << '\n';
    }


    return 0;
}