#include <fstream>
#include <cstring>
#include <vector>
#include <stack>
using namespace std;
bool viz[100002];
int n,m,comp=0,ctc[100002],j;
vector<int>G[100002],GT[100002],v[100002];
stack<int>S;
void CA(int x)
{
    viz[x]=1;
    for(int i=0;i<G[x].size();i++)
    if(!viz[G[x][i]]) CA(G[x][i]);
    S.push(x);
}
void CA2(int x)
{
    ctc[x]=comp;
    for(int i=0;i<GT[x].size();i++)
    if(!ctc[GT[x][i]]) CA2(GT[x][i]);

}
int main()
{
    int x,y,i;
    ifstream fi("ctc.in");
    ofstream fo("ctc.out");
    fi>>n>>m;
    for(i=1;i<=m;i++)
    {
        fi>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    if(!viz[i]) CA(i);
    while(!S.empty())
    {
        while(!S.empty() and ctc[S.top()]) S.pop();
        if(S.empty()) break;
        x=S.top(); S.pop();
        comp++;
        CA2(x);
    }
    for(i=1;i<=n;i++)
    v[ctc[i]].push_back(i);
    fo<<comp<<"\n";
    for(i=1;i<=comp;i++)
    {
        for(j=0;j<v[i].size();j++)
        fo<<v[i][j]<<" ";
        fo<<"\n";
    }
    return 0;
}