#include <iostream>
#include <stdio.h>
#include <vector>

using namespace std;

vector <int> g[100010];
vector <int> invers[100010];
vector <int> postordine;
vector <int> sol[100010];
int m,n,s,viz[100010],vizinvers[100010];

void citire()
{
    freopen("ctc.in","r",stdin);
    scanf("%d %d",&n,&m);
    for(int i=0; i<m; i++)
    {
        int a,b;
        scanf("%d %d",&a,&b);
        g[a].push_back(b);
        invers[b].push_back(a);
    }
}

void dfs(int k)
{
    for(int i=0; i<g[k].size(); i++)
        if(!viz[g[k][i]])
        {
            viz[g[k][i]]=1;
            dfs(g[k][i]);
        }
    postordine.push_back(k);
}

void dfsctc(int k)
{
    sol[s].push_back(k);
    for(int i=0; i<invers[k].size(); i++)
        if(!vizinvers[invers[k][i]])
        {
            vizinvers[invers[k][i]]=1;
            dfsctc(invers[k][i]);
        }
}

int main()
{
    freopen("ctc.out","w",stdout);
    citire();
    for(int i=1; i<=n; i++)
        if(!viz[i])
        {
            viz[i]=1;
            dfs(i);
        }
    for(int i=postordine.size()-1; i>=0; i--)
        if(!vizinvers[postordine[i]])
        {
            s++;
            vizinvers[postordine[i]]=1;
            dfsctc(postordine[i]);
        }
    printf("%d\n",s);
    for(int i=1;i<=s;i++)
    {
        for(int j=0;j<sol[i].size();j++)
            printf("%d ",sol[i][j]);
        printf("\n");
    }
    return 0;
}