#include <vector>
#include <stack>
#include <cstdio>
#define nmax 100010
#define pb push_back
#define min(a,b) ( (a)<(b)? (a) : (b) )
using namespace std;

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

void tarjan(int n)
{
    index++;
    idx[n]=index; lowlink[n]=index;
    s.push(n); ins[n]=1;
    vector<int>::iterator it;

    for(it=m[n].begin();it!=m[n].end();it++)
    if(!idx[*it]) { tarjan(*it); lowlink[n]=min(lowlink[n],lowlink[*it]);}
    else if(ins[*it]) lowlink[n]=min(lowlink[n],idx[*it]);

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

int main()
{
    int n1,n2;
    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].pb(n2);
    }
    for(int i=1;i<=n;i++)
        if(!idx[i]) tarjan(i);
    printf("%d\n",sol.size());
    for(int i=0;i<sol.size();i++)
    {
        for(int j=0;j<sol[i].size();j++) printf("%d ",sol[i][j]);
        printf("\n");
    }
    fclose(stdin);
    fclose(stdout);
    return 0;
}

/*void tarjan(int v)
{
    index++;
    idx[v]=index; lowlink[v]=index;
    s.push(v); in_stack[v]=1;
    vector<int>::const_iterator it;

    for(it=vert[v].begin();it!=vert[v].end();it++)
        if(idx[*it]==0) { tarjan(*it); lowlink[v]=minim(lowlink[v],lowlink[*it]); }
        else if(in_stack[*it]) lowlink[v]=minim(lowlink[v],lowlink[*it]);

    if(lowlink[v]==idx[v])
    {
        ctc.clear();
        int node;
        do
        {
            ctc.push_back(node=s.top()); s.pop(); in_stack[node]=0;
        }while(node!=v);
        sol.push_back(ctc);
    }
}

int main()
{
    int n1,n2,j;
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(;m;m--)
    {
        scanf("%d%d",&n1,&n2);
        vert[n1].push_back(n2);
    }
    for(int i2=1;i2<=n;i2++)
        if(idx[i2]==0) tarjan(i2);

    printf("%d\n",sol.size());
    for(int 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;
}*/