#include <cstdio>
#include <vector>

#define NMAX 100007

using namespace std;
int n, m, topo[NMAX], ct, viz[NMAX], a, b;
struct component
{
    vector <int> mem;
} tmp;
vector <int> adj[NMAX], adjp[NMAX];
vector <component> ans;

void citire()
{
    scanf("%d %d", &n, &m);
    for(; m; --m)
    {
        scanf("%d %d", &a, &b);
        adj[a].push_back(b);
        adjp[b].push_back(a);
    }
}
void dfs(int nod)
{
    viz[nod] = 1;
    int sze = adj[nod].size();
    for(int i = 0; i< sze; ++i)
    {
        if(!viz[adj[nod][i]])
        {
            dfs(adj[nod][i]);
        }
    }
    ct++;
    topo[ct] = nod;
}
void sort_topo()
{
    for(int i = 1; i<= n;++i)
    {
        if(!viz[i])
        {
            dfs(i);
        }
    }
}
void componenta(int nod)
{
    viz[nod] = 0;
    tmp.mem.push_back(nod);
    int sze = adjp[nod].size();
    for(int i = 0; i< sze; ++i)
    {
        if(viz[adjp[nod][i]])
        {
            componenta(adjp[nod][i]);
        }
    }
}
void kosaraju()
{
    while(ct)
    {
        int val = topo[ct];
        --ct;
        if(!viz[val]) continue;
        tmp.mem.clear();
        componenta(val);
        ans.push_back(tmp);
    }
}
void afisare()
{
    int sze = ans.size();
    printf("%d\n", sze);
    for(int i = 0; i< sze; ++i)
    {
        int sze1 = ans[i].mem.size();
        for(int j = 0; j< sze1; ++j)
        {
            printf("%d ", ans[i].mem[j]);
        }
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    citire();
    sort_topo();
    kosaraju();
    afisare();
    return 0;
}