# include <bits/stdc++.h>

using namespace std;

const int nmax = 1e5 + 5;

vector <int> G[nmax], G2[nmax];

bool sel[nmax];
int st[nmax], n, m, N;

void dfs(int node)
{
    sel[node] = true;

    for (auto &it: G[node])
        if (!sel[it]) dfs(it);

    st[++N] = node;
}

void dfs2(int node, bool afis)
{
    sel[node] = true;

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

    for (auto &it: G2[node])
        if (!sel[it]) dfs2(it, afis);

}

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

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

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

    for (int i = 1; i <= n; ++i)
        if (!sel[i]) dfs(i);

    int nr = 0;

    memset(sel, false, sizeof(sel));

    for (int i = n; i >= 1; --i)
        if (!sel[st[i]])
        {
            ++nr;
            dfs2(st[i], false);
        }

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

    memset(sel, false, sizeof(sel));

    for (int i = n; i >= 1; --i)
        if (!sel[st[i]])
        {
            dfs2(st[i], true);
            printf("\n");
        }

    return 0;
}