#include <cstdio>
#include <vector>
#include <stack>
using namespace std;

int n,indax=1,nrsol=0;
vector<int> a[100001],idx,low,comp;
vector< vector<int> > sol;
vector<bool> instack;
stack<int> s;
void readData(){
    int i,m,x,y;
    freopen("ctc.in","r",stdin);
    scanf("%d %d",&n,&m);
    for(i=0;i<m;++i){
        scanf("%d %d",&x,&y);
        a[x].push_back(y);
    }
    idx.resize(n+1);
    idx.assign(n+1,-1);
    low.resize(n+1);
    instack.resize(n+1);
    instack.assign(n+1,false);
}


void ctc(int x){
    idx[x]=low[x]=indax;
    ++indax;
    s.push(x); instack[x]=true;
    vector<int>::iterator it;
    for(it=a[x].begin();it!=a[x].end();++it)
        if(idx[*it]==-1){
            ctc(*it);
            low[x]=min(low[x],low[*it]);
        }
        else if(instack[*it])
            low[x]=min(low[x],low[*it]);
    if(idx[x]==low[x]){
        ++nrsol;
        comp.clear();
        int nod;
        do{ nod=s.top();
            comp.push_back(nod);
            s.pop();
            instack[nod]=false;
        } while(nod!=x);

        sol.push_back(comp);
    }
}

void writeData(){
    unsigned int i,j;
    freopen("ctc.out","w",stdout);
    printf("%d\n",nrsol);
    for(i=0;i<sol.size();++i){
        for(j=0;j<sol[i].size();++j)
            printf("%d ",sol[i][j]);
        printf("\n");
    }
}

int main()
{
    readData();
    for(int i=1;i<=n;++i)
        if(idx[i]==-1)
            ctc(i);
    writeData();
    return 0;
}