#include <cstdio>
#include <vector>

#define MAXN (int)1e5

int N, M;
std::vector <int> v[MAXN + 1], inv[MAXN + 1];
bool viz[MAXN + 1];
std::vector <int> sol;

void topodfs(int nod)  {
    if(viz[nod])
        return;
    viz[nod] = 1;
    for(auto x : v[nod])  {
        topodfs(x);
    }
    sol.push_back(nod);
}

std::vector <int> ans[MAXN + 1];
int cnt;

void dfs(int nod)  {
    if(!viz[nod])
        return;
    viz[nod] = 0;
    for(auto &x : inv[nod])  {
        dfs(x);
    }
    ans[cnt].push_back(nod);
}

int main()  {
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    cin >> N >> M;
    for(int i = 1;i <= M;i++)  {
        int x, y;
        cin >> x >> y;
        v[x].push_back(y);
        inv[y].push_back(x);
    }
    for(int i = 1;i <= N;i++)
        topodfs(i);
    for(int i = sol.size() - 1;i >= 0;i--)  {
        if(viz[sol[i]])  {
            dfs(sol[i]);
            cnt++;
        }
    }
    cout << cnt << "\n";
    for(int i = 0;i < cnt;i++)  {
        for(auto x : ans[i])
            cout << x << " ";
        cout << "\n";
    }
    return 0;
}//Pai ce ma m-am tampit?