# include <bits/stdc++.h>

using namespace std;

const int Nmax = 100000 + 5;

int n, m, N = 0, S = 0, x, y;

int st[Nmax], sol[Nmax];
bool ap[Nmax];

vector <int> G1[Nmax], G2[Nmax];

void read()
{
    for (int i = 1; i <= m; ++i)
    {
        scanf("%d %d\n", &x, &y);
        G1[x].push_back(y), G2[y].push_back(x);
    }
}

void DFS (int node)
{

    ap[node] = true;

    for (int i = 0; i < G1[node].size(); ++i)
        if (!ap[G1[node][i]]) DFS(G1[node][i]);

    st[++N] = node;

}

void DFT(int node, bool afis)
{
    ap[node] = true;

    if (afis == true) printf("%d ", node);

    for (int i = 0; i < G2[node].size(); ++i)
        if (!ap[G2[node][i]]) DFT(G2[node][i], afis);

}

int main ()

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

    int i;

    scanf("%d %d\n", &n, &m);

    read();

    for (i = 1; i <= n; ++i)
        if (!ap[i]) DFS(i);

    memset(ap, false, sizeof(ap));

    int nr = 0;

    for (i = n; i >= 1; --i)
    {
        if (!ap[st[i]])
        {
            DFT(st[i], false);
            ++nr;
        }
    }

    printf("%d\n", nr);

    memset(ap, false, sizeof(ap));

    for (i = n; i >= 1; --i)
    {
        if (!ap[st[i]])
        {
            DFT(st[i], true);
            printf("\n");
        }
    }


    return 0;
}