#include<bits/stdc++.h>

using namespace std;

const int nmax=100005;

vector <int> g[nmax];
vector <int> gt[nmax];
vector <int> con[nmax];

int visited[nmax+1];
int srt[nmax+1];
int x, com_conex;

void dfs(int nod)
{
    visited[nod]=1;
    for(int i=0; i<g[nod].size(); i++)
        if(visited[g[nod][i]]==0)
            dfs(g[nod][i]);
    srt[x++]=nod;
}

void dfs2(int nod)
{
    visited[nod]=2;
    for(int i=0; i<gt[nod].size(); i++)
        if(visited[gt[nod][i]]!=2)
            dfs2(gt[nod][i]);
    con[com_conex].push_back(nod);
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int n, m, y;

    scanf("%d%d", &n, &m);
    for(int i=1; i<=m; i++)
    {
        scanf("%d%d", &x, &y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    x=0;
    for(int i=1; i<=n; i++)
        if(visited[i]==0)
            dfs(i);
    for(int i=n-1; i>=0; i--)
    {
        if(visited[srt[i]]!=2)
        {
            ++com_conex;
            dfs2(srt[i]);
        }
    }
    printf("%d\n", com_conex);
    for(int i=1; i<=com_conex; i++)
    {
        for(int j=0; j<con[i].size(); j++)
            printf("%d ", con[i][j]);
        printf("\n");
    }

    return 0;
}