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


vector <int> g[100005],gt[100005],post_ordine,ctc[100005];
int viz[100005],nr,n,m,x,y;


void dfs(int vf)
{
    viz[vf]=1;
    vector <int> ::iterator it;
    for(it=g[vf].begin();it!=g[vf].end();it++)
    {
        if(!viz[*it])
            dfs(*it);
    }
    post_ordine.push_back(vf);
}


void dfst(int vf)
{
    viz[vf]=0;
    ctc[nr].push_back(vf);
    vector <int> ::iterator it;
    for(it=gt[vf].begin();it!=gt[vf].end();it++)
    {
        if(viz[*it])
            dfst(*it);
    }
}



int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    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);
    }
    for(int i=1;i<=n;i++)
    {
        if(!viz[i])
        {
            dfs(i);
        }
    }
    for(int i=post_ordine.size()-1;i>=0;i--)
    {
        if(viz[post_ordine[i]])
            {
                nr++;
                dfst(post_ordine[i]);
            }

    }
    printf("%d\n",nr);
    for(int i=1;i<=nr;i++)
    {
        vector <int> :: iterator it;
        for(it=ctc[i].begin();it!=ctc[i].end();it++)
        {
            printf("%d ",*it);
        }
        printf("\n");
    }
    return 0;
}