#include <bits/stdc++.h>

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

const int NMax = 100001;

vector<int> ans[NMax];
vector<int> G[NMax],GT[NMax];
int nr,m,n,x,y,top;
int viz[NMax],s[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]);
        }
    }
    s[++top] = nod;
}
void dfsT(int nod){
    viz[nod] = 1;
    ans[nr].push_back(nod);
    for(int i = 0; i < GT[nod].size(); ++i){
        if(!viz[GT[nod][i]]){
            dfsT(GT[nod][i]);
        }
    }
}
int main()
{
    f >> n >> m;
    for(int i = 1; i <= m; ++i){
        f >> 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[s[i]]){
            nr++;
            dfsT(s[i]);
        }
    }
    g << nr << '\n';
    for(int i = 1; i <= nr; ++i){
        for(int j = 0; j < ans[i].size(); ++j){
            g << ans[i][j] << ' ';
        }
        g << '\n';
    }
    return 0;
}