#include <bits/stdc++.h>
using namespace std;
#define LMAX 100005
int n;
bool Plus[LMAX];
vector<int> G[LMAX],GT[LMAX];
stack<int> st;
void dfs_plus(int nod){
    Plus[nod]=1;
    for(auto it : G[nod])
        if(!Plus[it])
            dfs_plus(it);
    st.push(nod);
}
bool Minus[LMAX];
int nr_comp=0;
vector<int> ctc[LMAX];
void dfs_minus(int nod){
    ctc[nr_comp].push_back(nod);
    Minus[nod]=1;
    for(auto it : GT[nod])
        if(!Minus[it])
            dfs_minus(it);
}
void Kosaraju(){
    for(int i=1;i<=n;++i)
        if(!Plus[i])
            dfs_plus(i);
    while(!st.empty()){
        int nod=st.top();
        st.pop();
        if(!Minus[nod]){
            ++nr_comp;
            dfs_minus(nod);
        }
    }
    printf("%d\n",nr_comp);
    for(int i=1;i<=nr_comp;++i){
        for(auto it : ctc[i])
            printf("%d ",it);
        printf("\n");
    }
}
int main(){
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int m;
    scanf("%d %d",&n,&m);
    for(int i=1;i<=m;++i){
        int from,to;
        scanf("%d %d",&from,&to);
        G[from].push_back(to);
        GT[to].push_back(from);
    }
    Kosaraju();
    return 0;
}