// Matteo Verzotti - C++
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <ctime>
#include <map>
#include <chrono>
#include <cmath>
#define INF 0x3f3f3f3f
#define MAX(a,b) a>b ? a:b
#define MIN(a,b) a<b ? a:b

using namespace std;

const int NODE = 1e5;

vector <int> g[NODE+5],gt[NODE+5],ctc[NODE+5];
stack <int> st;
bool viz[NODE+5];

int n, m, x, y, nrctc;

void DFS(int node) {
    viz[node] = 1;
    for(int i=0; i<g[node].size(); i++) {
        int vecin = g[node][i];
        if(!viz[vecin])
            DFS(vecin);
    }
    st.push(node);
}

void DFS2(int node) {
    viz[node] = 0;
    ctc[nrctc].push_back(node);
    for(int i=0; i<gt[node].size(); i++) {
        int vecin = gt[node][i];
        if(viz[vecin])
            DFS2(vecin);
    }
}

void solve() {
    for(int i=1; i<=n; i++)
        if(!viz[i])
            DFS(i);
    while(st.size()) {
        int node = st.top();
        if(viz[node]){
            DFS2(node);
            nrctc++;
        }
        st.pop();
    }
}

int main() {
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1; i<=m; i++) {
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    solve();
    printf("%d\n",nrctc);
    for(int i=0;i<nrctc;i++){
        for(int j=0;j<ctc[i].size();j++)
            printf("%d ",ctc[i][j]);
        printf("\n");
    }
    fclose(stdin);
    fclose(stdout);
    return 0;
}