#include <bits/stdc++.h>
using namespace std;
#define pb push_back

ifstream f("ctc.in");
ofstream g("ctc.out");

const int N = 1e5+5;

int n, k;
bitset<N> u;
stack<int> stk;
vector<vector<int>> G, GT, CTC;
void read(), dfsG(int), dfsGT(int);

int main()
{
    read();
    for (int i = 1; i <= n; i++)
        if (!u[i]) dfsG(i);
    u.reset();
    while (!stk.empty()){
        int nod = stk.top(); stk.pop();
        if (!u[nod]) {
            CTC.pb({});
            dfsGT(nod), k++;
        }
    }
    g << k << '\n';
    for (int i = 0; i < k; i++){
        for (auto v: CTC[i]) g << v << ' ';
        g << '\n';
    }

    return 0;
}

void read(){
    int m; f >> n >> m;
    G.resize(n+3); GT.resize(n+3);
    while (m--){
        int a, b; f >> a >> b;
        G[a].pb(b); GT[b].pb(a);
    }
}
void dfsG(int nod){
    u[nod] = 1;
    for (auto v: G[nod])
        if(!u[v]) dfsG(v);
    stk.push(nod);
}
void dfsGT(int nod){
    u[nod] = 1; CTC[k].pb(nod);
    for (auto v: GT[nod])
        if (!u[v]) dfsGT(v);
}