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

using namespace std;

vector<int> g[100001];
stack<int> st;

struct V
{
    int index;
    int lowlink;
};

V v[100001];
int sol[100001];
int index = 0;
bool in_stack[100001];
bool new_line[100001];
int nr_sol = 0;

void scc(int x)
{
    in_stack[x] = 1;
    st.push(x);
    v[x].index = ++index;
    v[x].lowlink = index;
    for (int i = 0; i < g[x].size(); ++i)
        if (v[g[x][i]].index == 0)
        {
            scc(g[x][i]);
            v[x].lowlink = min(v[x].lowlink, v[g[x][i]].lowlink);
        }
        else
            if (in_stack[g[x][i]])
            {
                v[x].lowlink = min(v[x].lowlink, v[g[x][i]].index);
            }
    if (v[x].index == v[x].lowlink)
    {
        ++nr_sol;
        new_line[sol[0]+1] = 1;
        if (x != st.top())
        {
            sol[++sol[0]] = st.top();
            in_stack[st.top()] = 0;
            st.pop();
            while (x != st.top())
            {
                sol[++sol[0]] = st.top();
                in_stack[st.top()] = 0;
                st.pop();
            }
        }
        sol[++sol[0]] = st.top();
        in_stack[st.top()] = 0;
        st.pop();
    }
}

int main()
{
    FILE *in = fopen("ctc.in", "r");
    FILE *out = fopen("ctc.out", "w");

    int n, m;
    fscanf(in, "%d%d", &n, &m);
    for (int x, y; m > 0; --m)
    {
        fscanf(in, "%d%d", &x, &y);
        g[x].push_back(y);
    }

    for (int i = 1; i <= n; ++i)
        if (v[i].index == 0)
            scc(i);

    fprintf(out, "%d", nr_sol);
    for (int i = 1; i <= n; ++i)
        if (new_line[i])
            fprintf(out, "\n%d", sol[i]);
        else
            fprintf(out, " %d", sol[i]);
    fprintf(out, "\n");

    fclose(in);
    fclose(out);

    return 0;
}