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

using namespace std;
typedef int var;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

#define MAXN 100001

var n, m;
vector<var> G[MAXN];

var D[MAXN], LOW[MAXN];
bool VIZ[MAXN];
bool IN[MAXN];

var nr_ctc = 0;
stack<var> ST;
vector<var> CTC[MAXN];

var tm = 0;
void dfs(var node) {
    VIZ[node] = 1;
    D[node] = ++tm;
    LOW[node] = D[node];
    ST.push(node);
    IN[node] = 1;

    for(auto vec : G[node]) {
        if(!VIZ[vec]) {
            dfs(vec);
            LOW[node] = min(LOW[node], LOW[vec]);
        } else if(IN[vec]) {
            LOW[node] = min(LOW[node], D[vec]);
        }
    }

    if(LOW[node] == D[node]) {
        nr_ctc ++;
        while(ST.top() != node) {
            CTC[nr_ctc].push_back(ST.top());
            IN[ST.top()] = 0;
            ST.pop();
        }
        CTC[nr_ctc].push_back(node);
        IN[node] = 0;
        ST.pop();
    }
}

int main() {

    var a, b;

    var n, m;
    fin>>n>>m;
    while(m--) {
        fin>>a>>b;
        G[a].push_back(b);
    }

    dfs(1);

    fout<<nr_ctc<<'\n';
    for(var i=1; i<=nr_ctc; i++) {
        for(auto node : CTC[i]) {
            fout<<node<<" ";
        }
        fout<<'\n';
    }

    return 0;
}