#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 clr(A,x) memset(A, x, sizeof(A))
#define cpy(A,B) memcpy(A, B, sizeof(B))
#define g(stream, s) getline(stream, s)
#define FASTIO ios_base::sync_with_stdio(0)
typedef long long ll;
typedef unsigned long long ull;
using namespace std;

const int CHARMAX = (1 << 10);
const int INFINT = 2000000000 + 100;
const ll INFLL = (1LL << 62);

/*class InParsare
{
private:
    FILE *fin;
    char *buffer;
    size_t index_of_buffer;

    char read_character()
    {
        index_of_buffer++;
        if(index_of_buffer == CHARMAX)
        {
            fread(buffer, 1, CHARMAX, fin);
            index_of_buffer = 0;
        }
        return buffer[index_of_buffer];
    }

public:
    InParsare(const char *name)
    {
        fin = fopen(name, "r");
        buffer = new char[CHARMAX]();
        index_of_buffer = CHARMAX - 1;
    }

    template<class T>
    InParsare &operator >> (T &n)
    {
        char c;
        while(!isdigit(c = read_character()) && c != '-');

        int sgn = 1;
        if(c == '-')
        {
            n = 0;
            sgn = -1;
        }
        else n = c - '0';

        while(isdigit(c = read_character()))
            n = n * 10 + c - '0';
        n *= sgn;

        return *this;
    }
};

class OutParsare
{
private:
    FILE *fout;
    char *buffer;
    size_t index_of_buffer;

    void write_character(char character)
    {
        if(index_of_buffer == CHARMAX)
        {
            fwrite(buffer, 1, CHARMAX, fout);
            index_of_buffer = 0;
            buffer[index_of_buffer++] = character;
        }
        else buffer[index_of_buffer++] = character;
    }

public:

    OutParsare(const char *name)
    {
        fout = fopen(name, "w");
        buffer = new char[CHARMAX]();
        index_of_buffer = 0;
    }

    ~OutParsare()
    {
        fwrite(buffer, 1, index_of_buffer, fout);
        fclose(fout);
    }
    template<class T>
    OutParsare &operator << (T n)
    {
        if(typeid(T).name() == typeid(char).name())
        {
            write_character(n);
            return *this;
        }

        if(n <= 9)
            write_character(n + '0');
        else
        {
            (*this) << (n / 10);
            write_character(n % 10 + '0');
        }

        return *this;
    }

};*/

//InParsare fin("zoo.in"); /// merg numai pt numere
//OutParsare fout("zoo.out"); /// merg numai pt numere + caractere individuale, nu stringuri
ifstream fin("ctc.in");
ofstream fout("ctc.out");

const int NMAX = 1e5 + 1;
const int MOD = 666013;
const double EPS = 0.000000001;

int n, m;
V graf[NMAX];
int niv[NMAX], low[NMAX];
bool viz[NMAX];
int ttime = 1;

stack<int> s;
V temp;
vector<V> sol;

void tarjan(int nod)
{
    niv[nod] = low[nod] = ttime++;
    viz[nod] = 1;
    s.push(nod);

    for(auto i: graf[nod])
        if(niv[i] == 0)
        {
            tarjan(i);
            low[nod] = min(low[nod], low[i]);
        }
        else if(viz[i])
            low[nod] = min(low[nod], low[i]);

    if(low[nod] == niv[nod])
    {
        temp.clear();
        int a;
        do
        {
            a = s.top();
            s.pop();
            temp.pb(a);
            viz[a] = 0;
        }while(a != nod);
        sol.pb(temp);
    }
}

int main()
{
    fin >> n >> m;
    for1(i, m)
    {
        int a, b;
        fin >> a >> b;
        graf[a].pb(b);
    }
    for1(i, n)
        if(!niv[i])
            tarjan(i);//, cout << i << ' ';

    fout << sol.size() << '\n';
    for(auto it: sol)
    {
        for(auto i: it)
            fout << i << ' ';
        fout << '\n';
    }

    return 0;
}