#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
vector<int> g[100005];
vector<int> gt[100005];
vector<int> l;
bool viz[100005];
int cont;
vector<int> comp[100005];
void dfs(int nod)
{
    viz[nod]=1;
    for(int v : g[nod])
        if(!viz[v])
            dfs(v);
    l.push_back(nod);
}
void dfst(int nod)
{
    viz[nod]=1;
    for(int v : gt[nod])
        if(!viz[v])
            dfst(v);
    comp[cont].push_back(nod);
}
int main()
{   freopen("ctc.in", "r",stdin);
    freopen("ctc.out", "w",stdout);
    int n,m,i,x,y;
    scanf("%d%d", &n, &m);
    for(i=1; i<=m; i++){
        scanf("%d%d", &x, &y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for(i=1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    reverse(l.begin(), l.end());
    for(int u : l)
        viz[u]=0;
    for(int u : l){
        if(!viz[u]){
            cont++;
            dfst(u);
        }
    }
    printf("%d\n", cont);
    for(i=1; i<=cont; i++){
        for(int u : comp[i])
            printf("%d ", u);
        printf("\n");
    }
    return 0;
}