#include <iostream>
#include <fstream>
#include <stack>
#include <vector>

std::ifstream in("ctc.in");
std::ofstream out("ctc.out");

int n, m, ord = 0, count = 0;
bool marked[100005], in_stack[100005];
int order[100005], lowest[100005];
std::vector<int> g[100005], result[100005];
std::stack<int> st;

int tarjan(int node){
//    std::cout << "Marked node " << node << '\n';
    marked[node] = true;
    order[node] = lowest[node] = ++ord;
    st.push(node);
    in_stack[node] = true;

    for(int i = 0; i < g[node].size(); i++) {
        int new_node = g[node][i];
        if (!marked[new_node]) {
            tarjan(new_node);
//            std::cout << "Not marked: \n";
//            std::cout << node << " " << new_node << '\n';
//            std::cout << lowest[node] << " " << lowest[new_node] << '\n';
            lowest[node] = std::min(lowest[node], lowest[new_node]);
//            std::cout << lowest[node] << " " << lowest[new_node] << '\n' << '\n';

        }
        else if(in_stack[new_node]) {
//            std:: cout << "Marked: \n";
//            std:: cout << node << " " << new_node << '\n';
//            std:: cout << lowest[node] << " " << order[new_node] << '\n';
            lowest[node]=std::min(lowest[node],order[new_node]);
//            std:: cout << lowest[node] << " " << order[new_node] << '\n' << '\n';

        }
    }

    int w = 0;  // To store stack extracted vertices

    if (lowest[node] == order[node])
    {
        while (st.top() != node)
        {
            w = (int) st.top();
            result[count].push_back(w);
            in_stack[w] = false;
            st.pop();
        }
        w = (int) st.top();
        result[count].push_back(w);
        in_stack[w] = false;
        st.pop();

        count++;
    }
//    for(int i = 1; i <= n; i++)
//        std:: cout << i << " ";
//    std:: cout << "\n";
//    for(int i = 1; i <= n; i++)
//        std:: cout << order[i] << " ";
//    std:: cout << "\n";
//    for(int i = 1; i <= n; i++)
//        std:: cout << lowest[i] << " ";
//    std:: cout << "\n\n";

}

int main() {
    in >> n >> m;
    for (int i = 1; i <= m; i++) {
            int a, b;
            in >> a >> b;
            g[a].push_back(b);
        }

    tarjan(1);


    for(int i = 0; i < count; i++)
        std::sort(result[i].begin(),result[i].end());

    out << count << '\n';
    for(int i = 0; i < count; i++){
       for(int j = 0; j < result[i].size(); j++){
           out << result[i][j] << " ";
       }
       out << '\n';
    }

//    std:: cout << "\n\n";
//    for(int i = 1; i <= n; i++)
//        std:: cout << i << " ";
//    std:: cout << "\n";
//    for(int i = 1; i <= n; i++)
//        std:: cout << order[i] << " ";
//    std:: cout << "\n";
//    for(int i = 1; i <= n; i++)
//        std:: cout << lowest[i] << " ";


    return 0;
}