#include <cstdio>
#include <vector>
#include <bitset>
#include <stack>

#define Nmax 100005

using namespace std;
int N,M,ctc;

vector<int> G[Nmax],Gt[Nmax],ans[Nmax];
bitset<Nmax> used,mark;
stack<int> S;

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

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

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

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

    read();
    kosaraju();
    print();

    return 0;
}