#include <bits/stdc++.h>

using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
const int nMax = 100003;
vector <int> Graf[nMax], GrafT[nMax], Ans[nMax];
bool viz[nMax];
int St[nMax], dim, comp;
inline void FirstDfs(int nod) {
    viz[nod] = 1;
    for(auto i : Graf[nod]) {
        if(!viz[i]) {
            FirstDfs(i);
        }
    }
    St[++dim] = nod;
}
inline void SecondDfs(int nod) {
    viz[nod] = 1;
    Ans[comp].push_back(nod);
    for(auto i : GrafT[nod]) {
        if(!viz[i]) {
            SecondDfs(i);
        }
    }
}
int main()
{
    int n, m, x, y;
    f >> n >> m;
    for(int i = 1; i <= m; i++) {
        f >> x >> y;
        Graf[x].push_back(y);
        GrafT[y].push_back(x);
    }
    for(int i = 1; i <= n; i++) {
        if(!viz[i]) {
            FirstDfs(i);
        }
    }
    memset(viz, 0, sizeof viz);
    for(int k = dim; k >= 1; k--) {
        if(!viz[St[k]]) {
            comp++;
            SecondDfs(St[k]);
        }
    }
    g << comp << "\n";
    for(int i = 1; i <= comp; i++) {
        for(auto j : Ans[i]) {
            g << j << " ";
        }
        g << "\n";
    }
    return 0;
}