#include <iostream>
#include <vector>
#include <cstdio>
#include <bitset>
#include <stack>
using namespace std;
vector < int >graf1[100010],graf2[100010],aux;
bitset < 100010 > viz;
stack < int > st;
vector <vector<int> > raspuns;
int n,m;
void citire()
{
    scanf("%d%d",&n,&m);
    for(int i=1; i<=m; ++i)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        graf1[a].push_back(b);
        graf2[b].push_back(a);
    }
}
void dfs1(int i)
{
    viz[i]=1;
    vector < int >::iterator it;
    for(it=graf1[i].begin(); it!=graf1[i].end(); ++it)
    {
        if(!viz[*it])
        {
            dfs1(*it);
        }
    }
    st.push(i);
}
void dfs2(int i)
{
    viz[i]=1;
    aux.push_back(i);
    vector < int >::iterator it;
    for(it=graf2[i].begin(); it!=graf2[i].end(); ++it)
    {
        if(!viz[*it])
        {
            dfs2(*it);
        }
    }
}
void afisare()
{
    printf("%d\n", raspuns.size());

    for(int i = 0;i< raspuns.size();++i)
    {
        for(int j = 0;j<raspuns[i].size(); ++j)
            printf("%d ", raspuns[i][j]);
        printf("\n");
    }
}
int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    citire();
    for(int i=1; i<=n;++i)
        if(!viz[i])
            dfs1(i);
    viz=0;
    while(!st.empty())
    {
        int x=st.top();
        st.pop();
       if(viz[x])
            continue;
        aux.clear();
        dfs2(x);
        raspuns.push_back(aux);
    }
    afisare();
    return 0;
}