#include <bits/stdc++.h>

using namespace std;

const int NMax = 100005;

int n,m,top,ctc_nr,x,y;
int st[NMax],viz[NMax];
vector<int> G[NMax],GT[NMax],ctc[NMax];;

void dfs(int nod){
    viz[nod] = 1;
    for(int i = 0; i < G[nod].size(); ++i){
        if(!viz[G[nod][i]]){
            dfs(G[nod][i]);
        }
    }
    st[++top] = nod;
}
void dfsT(int nod){
    viz[nod] = 1;
    for(int i = 0; i < GT[nod].size(); ++i){
        if(!viz[GT[nod][i]]){
            dfsT(GT[nod][i]);
        }
    }
    ctc[ctc_nr].push_back(nod);
}
int main(){
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    cin >> n >> m;
    for(int i = 1; i <= m; ++i){
        cin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i = 1; i <= n; ++i){
        if(!viz[i]){
            dfs(i);
        }
    }
    memset(viz,0,sizeof(viz));
    for(int i = top; i >= 1; --i){
        if(!viz[st[i]]){
            dfsT(st[i]);
            ctc_nr++;
        }
    }
    cout << ctc_nr << '\n';
    for(int i = 0;i < ctc_nr; ++i){
        for(int j = 0; j < ctc[i].size(); ++j){
            cout << ctc[i][j] << ' ';
        }
        cout << '\n';
    }
    return 0;
}