#include <cstdio>
#include <deque>
#include <vector>
#include <algorithm>
using namespace std;
deque<int> st;
vector<int> g[100005];
struct Nod
{
    int disc,low;
} v[100005];
vector<int> sol[100005];
bool viz[100005];
int nr,k;
void dfs(int nod)
{
    v[nod].disc=v[nod].low=++nr;
    st.push_back(nod);
    viz[nod]=1;
    for(int i=0; i<g[nod].size(); i++){
        if(viz[g[nod][i]]==0){
            dfs(g[nod][i]);
            v[nod].low=min(v[nod].low, v[g[nod][i]].low);
        }
        else
            v[nod].low=min(v[nod].low, v[g[nod][i]].disc);
    }
    if(v[nod].low==v[nod].disc){
        ++k;
        while(st.back()!=nod){
            sol[k].push_back(st.back());
            st.pop_back();
        }
        sol[k].push_back(nod);
        st.pop_back();
    }
}
int main()
{   freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int n,m,i,x,y,j;
    scanf("%d%d", &n, &m);
    for(i=1; i<=m; i++){
        scanf("%d%d", &x, &y);
        g[x].push_back(y);
    }
    for(i=1; i<=n; i++)
        if(v[i].disc==0)
            dfs(i);
    printf("%d\n", k);
    for(i=1; i<=k; i++){
        for(j=0; j<sol[i].size(); j++)
            printf("%d ", sol[i][j]);
        printf("\n");
    }
    return 0;
}