#include <iostream>
#include <cstdio>
#include <stack>
#include <vector>
#define nmax 100010
using namespace std;

int idx[nmax],lowlink[nmax],ins[nmax],index;
int n,m1;
vector<int> m[nmax],ctc;
stack<int> s;
vector< vector<int> > sol;

void tarjan(int nod)
{
    index++;
    int crt;
    idx[nod]=index; lowlink[nod]=index;
    s.push(nod); ins[nod]=1;
    for(vector<int>::iterator it=m[nod].begin();it!=m[nod].end();it++)
        if(!idx[*it])
        {
            tarjan(*it);
            lowlink[nod]=min( lowlink[nod],lowlink[*it]);
        } else if(ins[*it]) lowlink[nod]=min(lowlink[nod],lowlink[*it]);

    if(lowlink[nod]==idx[nod])
    {
        ctc.clear();
        do
        {
            crt=s.top(); s.pop();
            ctc.push_back(crt); ins[crt]=0;
        } while(crt!=nod);
        sol.push_back(ctc);
    }
}

int main()
{
    int n1,n2,i,j;
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m1);
    for(;m1;m1--)
    {
        scanf("%d%d",&n1,&n2);
        m[n1].push_back(n2);
    }
    for(i=1;i<=n;i++)
       if(!idx[i]) tarjan(i);
    printf("%d\n",sol.size());
    for(i=0;i<sol.size();i++)
    {
        for(j=0;j<sol[i].size();j++) printf("%d ",sol[i][j]);
        printf("\n");
    }
    fclose(stdin);
    fclose(stdout);
    return 0;
}