#include <bits/stdc++.h>
#define IOS ios :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define NMAX 100005

using namespace std;

FILE *fin = fopen("ctc.in" , "r");
FILE *fout = fopen("ctc.out" , "w");

vector <int> muchii1[NMAX] , muchii2[NMAX] , H;
int n , m;
bool viz[NMAX];

vector <vector <int> > ans;

void DFS1(int nod)
{
    viz[nod] = 1;
    for(int i = 0 ; i < muchii1[nod].size() ; i ++)
        if(!viz[muchii1[nod][i]])
            DFS1(muchii1[nod][i]);
    H.push_back(nod);
}

void DFS2(int nod)
{
    viz[nod] = 1;
    for(int i = 0 ; i < muchii2[nod].size() ; i ++)
        if(!viz[muchii2[nod][i]])
            DFS2(muchii2[nod][i]);
    ans.back().push_back(nod);
}

int main()
{
    fscanf(fin , "%d%d" , &n , &m);
    for(int i = 1 ; i <= m ; i ++)
    {
        int x , y;
        fscanf(fin , "%d%d" , &x , &y);
        muchii1[x].push_back(y);
        muchii2[y].push_back(x);
    }
    for(int i = 1 ; i <= n ; i ++)
        if(!viz[i])
            DFS1(i);
    memset(viz , 0 , sizeof(viz));
    for(int i = H.size() - 1 ; i >= 0 ; i --)
        if(!viz[H[i]])
        {
            ans.push_back(vector <int> ());
            DFS2(H[i]);
        }
    fprintf(fout , "%d\n" , ans.size());
    for(int i = 0 ; i < ans.size() ; i ++)
    {
        for(int j = 0 ;  j < ans[i].size() ; j ++)
            fprintf(fout , "%d " , ans[i][j]);
        fprintf(fout , "\n");
    }
    return 0;
}