#include<stdio.h>
#include<vector>
#define Nmx 100001

using namespace std;

vector<int> GT[Nmx],G[Nmx],sol[Nmx];
int n,m,viz[Nmx],nrs,pre[Nmx],nr;

void citire()
{
    int x,y;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d",&x,&y);
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int x)
{
    vector<int>::iterator it;
    viz[x]=1;
    for(it=G[x].begin();it!=G[x].end();++it)
        if(!viz[*it])
            dfs(*it);
    pre[++nr]=x;
}

void dfst(int x)
{
    vector<int>::iterator it;
    sol[nrs].push_back(x);
    viz[x]=0;
    for(it=GT[x].begin();it!=GT[x].end();++it)
        if(viz[*it])
            dfst(*it);
}

void solve()
{
    for(int i=1;i<=n;++i)
        if(!viz[i])
            dfs(i);
    for(int i=n;i>=1;--i)
        if(viz[pre[i]])
        {
            ++nrs;
            dfst(pre[i]);
        }
    vector<int>::iterator it;
    printf("%d\n",nrs);
    for(int i=1;i<=nrs;++i)
    {
        for(it=sol[i].begin();it!=sol[i].end();++it)
            printf("%d ",*it);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    solve();
    return 0;
}