#include <cstdio>
#define Nmax 100010
#define pb push_back
#include <vector>
#include <cstring>

using namespace std;

vector <int> g[Nmax],gt[Nmax],ctc[Nmax];
int n,m,i,x,y,c[Nmax],nr,sol;
bool sel[Nmax];

void load()
{
    scanf("%d %d", &n, &m);
    for (int i=1;i<=m;++i)
     {
         scanf("%d %d", &x, &y);
         g[x].pb(y);
         gt[y].pb(x);
     }
}

inline void dfs(int x)
 {
     int i;
     sel[x]=true;
     for (i=0;i<g[x].size();++i)
      if (!sel[g[x][i]])
       dfs(g[x][i]);

    c[++nr]=x;
 }

inline void dfst(int x)
 {
     int i;
     sel[x]=true;
     for (i=0;i<gt[x].size();++i)
      if (!sel[gt[x][i]]) dfst(gt[x][i]);

     ctc[sol].pb(x);
 }

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);

    load();

    for (i=1;i<=n;++i)
     if (!sel[i]) dfs(i);

    memset(sel,0,sizeof(sel));

    for (i=n;i>=1;--i)
     if (!sel[c[i]])
      {
          ++sol;
          dfst(c[i]);
      }


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

    return 0;
}