#include <bits/stdc++.h>

using namespace std;

ifstream F("ctc.in");
ofstream G("ctc.out");

int n, m, x, y, K;
vector<int> a[100005], inv[100005], w[100005];
stack<int> st;
bool v[100005];

void dfs(int nod){
    v[nod] = 1;
    for(auto it:a[nod]){
        if(!v[it]) dfs(it);
    }
    st.push(nod);
}

void dfs1(int nod){
    v[nod] = 0;
    for(auto it:inv[nod]){
        if(v[it]) dfs1(it);
    }
    w[K].push_back(nod);
}

int main()
{
    F >> n >> m;
    for(int i = 1; i <= m; ++ i){
        F >> x >> y;
        a[x].push_back(y);
        inv[y].push_back(x);
    }
    for(int i = 1; i <= n; ++ i)
        if(!v[i]) dfs(i);
    while(!st.empty()){
        x = st.top();
        if(v[x]){
            ++K;
            dfs1(x);
        }
        st.pop();
    }
    G << K << '\n';
    for(int i = 1; i <= n; ++ i){
        for(auto it: w[i]) G << it<< " ";
        G << '\n';
    }
    return 0;
}