#include<bits/stdc++.h>
#pragma GCC optimize("Ofast,unroll-loops,inline")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define setinf(x) memset(x,0x3f3f3f3f,sizeof(x));
#define set0(x) memset(x,0,sizeof(x));
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define INF 0x3f3f3f3f
#define vi vector<int>
#define ll long long
#define vll vector<ll>
#define pb push_back
#define fi first
#define se second
#define DD 100001
#define nl '\n'
using namespace std;
const string file="ctc";
ifstream f(file+".in");
ofstream g(file+".out");
//#define f cin
//#define g cout
int n,m;
vi v[DD],vv[DD];
stack<int>s;
int fr[DD];
int cnt;
vector<vi>r;
vi c;
void dfs(int x) {
    fr[x]=1;
    for (auto e:v[x])
        if (!fr[e]) dfs(e);
    s.push(x);
}
void Dfs(int x) {
    c.pb(x);
    fr[x]=1;
    for (auto e:vv[x])
        if (!fr[e]) Dfs(e);
}
int main(){
    f>>n>>m;
    for (int i=1; i<=m; ++i) {
        int x,y;
        f>>x>>y;
        v[x].pb(y);
        vv[y].pb(x);
    }
    for (int i=1; i<=n; ++i) {
        if (!fr[i]) {
            dfs(i);
        }
    }
    set0(fr);
    while (!s.empty()) {
        int x=s.top();
        s.pop();
        if (!fr[x]) {
            ++cnt;
            c.clear();
            Dfs(x);
            r.pb(c);
        }
    }
    g<<cnt<<nl;
    for (auto e:r) {
        for (auto ee:e) g<<ee<<' ';
        g<<nl;
    }
    system("pause");
    return 0;
}