#include<cstdio>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<iterator>
using namespace std;
FILE*in=fopen("ctc.in","r");
FILE*out=fopen("ctc.out","w");
int n,m,i,x,y,ct,j;
bool viz[100005];
int comp[100005];
stack<int> s;
vector<int> v[100005],rev[100005],ras[100005];
vector<int>::iterator it;
void dfs(int nod)
{
    viz[nod]=1;
    for(vector<int>::iterator it=v[nod].begin();it!=v[nod].end();++it)
    {
        if(viz[*it]==0)
        {
            dfs(*it);
        }
    }
    s.push(nod);
}
void ctcf(int nod)
{
    ras[ct].push_back(nod);
    viz[nod]=1;
    for(vector<int>::iterator it=rev[nod].begin();it!=rev[nod].end();++it)
    {
        if(viz[*it]==0)
        {
            ctcf(*it);
        }
    }
}
int main()
{
    fscanf(in,"%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        fscanf(in,"%d%d",&x,&y);
        v[x].push_back(y);
        rev[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            dfs(i);
        }
    }
    memset(viz,0,sizeof(viz));
    ct=0;
    while(!s.empty())
    {
        ctcf(s.top());
        s.pop();
        while(!s.empty()&&viz[s.top()]==1)
        {
            s.pop();
        }
        ct++;
    }
    fprintf(out,"%d\n",ct);
    for(i=0;i<ct;i++)
    {
        for(j=0;j<ras[i].size();j++)
        {
            fprintf(out,"%d ",ras[i][j]);
        }
        fprintf(out,"\n");
    }
}