#include <bits/stdc++.h>
#define DMAX 100010

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector <int>g[DMAX];
vector <int>gt[DMAX];
vector <int>afis[DMAX];

bool uz[DMAX];
int n,m,lg,nr;
int s[DMAX];

void citire();
void dfs(int node);
void dfs1(int node);

int main()
{int i,j;
 citire();
 for(i=1;i<=n;i++)
     if(!uz[i])
         dfs(i);
 while(lg>0)
       {if(uz[s[lg]])
           {nr++;
            dfs1(s[lg]);
           }
        lg--;
       }
 fout<<nr<<'\n';
 for(i=1;i<=nr;i++)
     {for(j=0;j<afis[i].size();j++)
          fout<<afis[i][j]<<' ';
      fout<<'\n';
     }
 return 0;
}
void citire()
{int i,j,x,y;
 fin>>n>>m;
 for(i=1;i<=m;i++)
    {fin>>x>>y;
     g[x].push_back(y);
     gt[y].push_back(x);
    }
}
void dfs(int node)
{int i;
 uz[node]=true;
 for(i=0;i<g[node].size();i++)
     if(!uz[g[node][i]])
        dfs(g[node][i]);
 s[++lg]=node;
}
void dfs1(int node)
{int i;
 uz[node]=false;
 afis[nr].push_back(node);
 for(i=0;i<gt[node].size();i++)
     if(uz[gt[node][i]])
        dfs1(gt[node][i]);
}