#include <iostream>
#include <cstdio>
#include <vector>
#define len 100005
using namespace std;

int n,m,viz[len],ass[len],k;

vector <int > g[len], L, com[len],gb[len];

void citire()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        gb[y].push_back(x);
    }
}
void visit(int nod) ///se ordoneaza in functie de vecini practic
{
    viz[nod]=1;
    for (vector <int > :: iterator it = g[nod].begin();it!=g[nod].end();++it)
        if (!viz[*it])
            visit(*it);
    L.push_back(nod);
}
void assig(int nod) ///ii atasez de o radacina
{
    ass[nod]=1;
    com[k].push_back(nod);
    for (vector <int > :: iterator it = gb[nod].begin();it!=gb[nod].end();++it)
        if (!ass[*it])
            assig(*it);
}
void kosaraju()
{
    for (int i=1;i<=n;++i)
        if (!viz[i])
            visit(i);
    while (!L.empty())
        {
            int v=L.back();
            if (!ass[v])
            {
                assig(v);
                ++k;
            }
            L.pop_back();
        }
    printf("%d\n",k);
    sort(com);
    for (int i=0;i<k;++i)
    {
        for (vector <int > :: iterator it = com[i].begin();it!=com[i].end();++it)
            printf("%d ",*it);
        printf("\n");
    }
}
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    kosaraju();
    return 0;
}