#include<stdio.h>
#include<vector>

using namespace std;

const int MAXN = 100001;

vector <int> g[MAXN], dfs_st;
bool viz[MAXN];
bool onS[MAXN];
int min_back[MAXN];
vector <vector <int>> sol;

FILE *in, *out;

void get_ctc(int v) {
    vector<int> rez = vector<int> ();
    while(dfs_st.back() != v) {
        rez.push_back(dfs_st.back());
        onS[dfs_st.back()] = false;
        dfs_st.pop_back();
    }

    rez.push_back(v);
    dfs_st.pop_back();
    onS[v] = false;
    sol.push_back(rez);
}

int tarj(int n) {


    viz[n] = true;
    min_back[n] = dfs_st.size();
    int poz = min_back[n];
    dfs_st.push_back(n);
    onS[n] = true;
    for(auto &it : g[n]) {
        if(!viz[it]) {
            int x = tarj(it);
            min_back[n] = min(min_back[n], x);
        } else {
            if(onS[it]) {
                min_back[n] = min(min_back[n], min_back[it]);
            }
        }
    }

    if(min_back[n] == poz) {
        get_ctc(n);
    }



    return min_back[n];
}




int main () {
    in = fopen("ctc.in", "r");
    out = fopen("ctc.out", "w");

    int n, m;
    fscanf(in, "%d %d", &n, &m);

    for(int i = 0; i < m; i++) {
        int x, y;
        fscanf(in, "%d %d", &x, &y);
        g[x].push_back(y);
    }

    fclose(in);

    for(int i = 1; i <= n; i++) {
        if(!viz[i]) {
            tarj(i);
        }
    }

    fprintf(out, "%d\n", sol.size());
    for(auto &ctc : sol) {
        for(auto &elem : ctc) {
            fprintf(out, "%d ", elem);
        }
        fprintf(out, "\n");
    }

    fclose(out);

    return 0;
}