#include <bits/stdc++.h>
#define N 100005

using namespace std;

ifstream f ("ctc.in");
ofstream g ("ctc.out");

int n , m , x , y;
vector < int > a[N] , b[N] , c[N];
stack < int > s;
short seen[N];

void dfs(int nod)
{
    seen[nod] = 1;

    for(int i = 0 ; i < a[nod].size() ; i++)
    {
        if(!seen[a[nod][i]])
            dfs(a[nod][i]);
    }

    s.push(nod);
}

void dfst(int nod , int ctc)
{
    seen[nod] = 2;
    c[ctc].push_back(nod);

    for(int i = 0 ; i < b[nod].size() ; i++)
    {
        if(seen[b[nod][i]] == 1)
            dfst(b[nod][i] , ctc);
    }
}

int main()
{
    int i , j , ctc = 0;

    f >> n >> m;

    for(i = 1 ; i <= m ; i++)
    {
        f >> x >> y;

        a[x].push_back(y);
        b[y].push_back(x);
    }

    for(i = 1 ; i <= n ; i++)
        if(!seen[i])
            dfs(i);


    while(!s.empty())
    {
        int nod = s.top();

        if(seen[nod] == 1)
        {
            ++ctc;
            dfst(nod , ctc);
        }

        s.pop();
    }

    g << ctc << '\n';

    for(i = 1 ; i <= ctc ; i++)
    {
        for(j = 0 ; j < c[i].size() ; j++)
            g << c[i][j] << ' ';

        g << '\n';
    }

    return 0;
}