#include <bits/stdc++.h>
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
int n, m, cc;
bitset <100001> viz;
vector <int> G[100001], Gt[100001], Comp[100001];
vector <int> sf;
void read();
void dfsw(int nod)///dfs ul pe g simplu
{
    viz[nod]=1;
    for(int i: G[nod])
        if(viz[i]==0)
            dfsw(i);
    sf.push_back(nod);///le adaugam in ordinea inversa i think
}
void dfsppp(int nod)///dfs pt graful trans
{
    viz[nod]=1;
    for(int i:Gt[nod])
        if(viz[i]==0)
            dfsppp(i);
    Comp[cc].push_back(nod);
}
int main()
{
    read();
    for(int i=1; i<=n; i++)
        if(viz[i]==0)
            dfsw(i);
    viz.reset();
    for(int i=n-1; i>=0; i--)
        if(viz[sf[i]]==0)
            ++cc, dfsppp(sf[i]);
    fout<<cc<<'\n';
    for(int i=1; i<=cc; i++){
        for(auto h: Comp[i])
            fout<<h<<" ";
        fout<<'\n';
    }
    return 0;
}
void read()
{
    fin>>n>>m;
    for(int i=1; i<=m; i++){
        int x, y;
        fin>>x>>y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
}