#include <cstdio>
#include <vector>
#include <bitset>
#include <stack>
#define Nmax 100005

using namespace std;
bitset<Nmax> used;
vector<int> G[Nmax],Gt[Nmax],ctc[Nmax];
stack<int> S;
int N,M,nctc;

void Read()
{
    scanf("%d%d",&N,&M);
    int a,b;
    for(int i = 1; i <= M; ++i){
        scanf("%d%d",&a,&b);
        G[a].push_back(b);
        Gt[b].push_back(a);
    }
}

void DFS(int k){
    used[k] = 1;
    for(vector<int>::iterator it = G[k].begin(); it != G[k].end();++it)
        if(!used[*it])
            DFS(*it);
    S.push(k);
}

void DFST(int k){
    used[k] = 1;
    ctc[nctc].push_back(k);
    for(vector<int>::iterator it = Gt[k].begin(); it != Gt[k].end(); ++it)
        if(!used[*it])
            DFST(*it);
}

void Solve()
{
    for(int i = 1; i <= N; ++i)
        if(!used[i])
            DFS(i);
    used = 0;
    while(!S.empty())
    {
        if(used[S.top()])
        {
            S.pop();
            continue;
        }
        ++nctc;
        DFST(S.top());
    }
}

void Print()
{
    printf("%d\n",nctc);
    for(int i = 1; i <= nctc; ++i)
    {
        for(vector<int>::iterator it = ctc[i].begin(); it != ctc[i].end(); ++it)
            printf("%d ",*it);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);

    Read();
    Solve();
    Print();

    return 0;
}