#include <stdio.h>
#include <string.h>
#include <vector>

#define maxN 131072

using namespace std;

int use[maxN];
int st[maxN];

vector <int> g[maxN];
vector <int> gt[maxN];
vector <int> ctc[maxN];

int sol=0;

inline void dfs(int nod)
{
    use[nod]=1;
    for(int i=0;i<g[nod].size();++i)
        if(!use[g[nod][i]]) dfs(g[nod][i]);

    st[++st[0]]=nod;
}

inline void dfst(int nod)
{
    use[nod]=1;
    for(int i=0;i<gt[nod].size();++i)
        if(!use[gt[nod][i]]) dfst(gt[nod][i]);

    ctc[sol].push_back(nod);
}

int main(int argc,char *argv[])
{
    int M,N,x,y;

    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);
    }

    memset(st,0,sizeof(st));
    memset(use,0,sizeof(use));

    for(int i=1;i<=N;++i)
        if(!use[i]) dfs(i);

    memset(use,0,sizeof(use));

    for(int i=N;i>0;--i)
        if(!use[st[i]])
        {
            ++sol;
            dfst(st[i]);
        }

    printf("%d\n",sol);
    for(int i=1;i<=sol;++i)
    {
        for(int j=0;j<ctc[i].size();++j)
            printf("%d ",ctc[i][j]);
        printf("\n");
    }

    return 0;
}