#include <cstdio>
#include <vector>
#define NMAX 100005
using namespace std;

vector <int> g[NMAX], gt[NMAX], postordine, ctc[NMAX]; /// graf, graf transpus
int viz[NMAX], n, m, nr; /// nr = nr componente tare conexe

void dfs(int vf)
{
    viz[vf] = 1;
    vector <int>::iterator it;
    for(it = g[vf].begin(); it < g[vf].end(); it++)
        if(!viz[*it])
            dfs(*it);
    postordine.push_back(vf);
}

void dfsgt(int vf)
{
    viz[vf] = 0;
    ctc[nr].push_back(vf);
    vector <int>::iterator it;
    for(it = gt[vf].begin(); it < gt[vf].end(); it++)
        if(viz[*it])
            dfsgt(*it);
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    scanf("%d %d", &n, &m);
    int x, y;
    for(int i = 1; i <= m; i++)
    {
        scanf("%d %d", &x, &y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if(!viz[i])
            dfs(i);
    for(int i = postordine.size()-1; i >= 0; i--)
        if(viz[postordine[i]])
        {
            nr++;
            dfsgt(postordine[i]);
        }
    printf("%d\n",nr);
    for(int i = 1; i <= nr; i++)
    {
        vector <int>::iterator it;
        for(it=ctc[i].begin(); it != ctc[i].end(); it++)
            printf("%d ", *it);
        printf("\n");
    }
    return 0;
}