#include <bits/stdc++.h>
#define NMAX 100009

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int>g[NMAX];

vector <int>afis[NMAX];
vector <int>gt[NMAX];
int  uz[NMAX];int i,lg,nr,n,j,m;int s[NMAX];void citire();void dfs(int k);void dfs1(int k);void reset();int main(){citire();for(i=1; i<=n; i++)if(!uz[i])dfs(i);reset();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 k)
{
    int i;
    uz[k]=1;
    for(i=0; i<g[k].size(); i++)
        if(!uz[g[k][i]])
        {
            dfs(g[k][i]);


        }
     s[++lg]=k;
}
void dfs1(int k)
{
    int i;
    uz[k]=nr;
    afis[nr].push_back(k);
    for(i=0; i<gt[k].size(); i++)
        if(!uz[gt[k][i]])
        {
            dfs1(gt[k][i]);


        }

}
void reset()
{
    int i;
    for(i=0; i<NMAX; i++)
        uz[i]=0;
}