#include <cstdio>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

vector<int> g[100005], gt[100005], aux;
vector< vector<int> > ans;
stack<int> s;
bool viz1[100005], viz2[100005];

void dfs1(int u)
{

    viz1[u] = 1;
    for(int i = 0; i < g[u].size(); i++)
        if(!viz1[g[u][i]]) dfs1(g[u][i]);
        s.push(u);
}

void dfs2(int u)
{

    viz2[u] = 1;
    for(int i = 0; i < gt[u].size(); i++)
        if(!viz2[gt[u][i]]) dfs2(gt[u][i]);
        aux.push_back(u);
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    int n, m, u, v;
    scanf("%d%d", &n, &m);
    for(int i = 0; i < m; i++)
    {
        scanf("%d%d", &u, &v);
        g[u].push_back(v);
        gt[v].push_back(u);
    }
    for(int i = 1; i <= n; i++) if(!viz1[i]) dfs1(i);
    while(!s.empty())
    {
        if(!viz2[s.top()]) aux.clear(), dfs2(s.top()), ans.push_back(aux);
        s.pop();
    }
    printf("%d\n", ans.size());
    for(int i = 0; i < ans.size(); i++)
    {
        sort(ans[i].begin(), ans[i].end());
        for(int j = 0; j < ans[i].size(); j++) printf("%d ", ans[i][j]);
        printf("\n");
    }
    return 0;
}