#include <bits/stdc++.h>
#define ff first
#define ss second

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;

const string file = "ctc";
const ll INF = 9223372036854775807ll;
const int inf = 2147483647, nmax = 100005;

int n, m, p, order[nmax];
vector<int> v[nmax], vt[nmax];
vector< vector<int> > sol;
bool ok[nmax];

void dfs(int x)
{
    ok[x] = 1;
    for(auto y : v[x])
        if(!ok[y])
            dfs(y);
    order[++p] = x;
}

void dfs2(int x)
{
    ok[x] = 0;
    sol.back().push_back(x);
    for (auto y : vt[x])
        if(ok[y])
            dfs2(y);
}

int main()
{
    ifstream fin (file+".in");
    ofstream fout (file+".out");
    fin >> n >> m;
    while(m--){
        int x, y;
        fin >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for (int i = 1; i <= n; ++i)
        if(!ok[i])
            dfs(i);
    for (int i = n; i >= 1; --i)
        if(ok[order[i]]){
            sol.push_back(vector<int>());
            dfs2(order[i]);
        }
    fout << sol.size() << "\n";
    for (auto x : sol){
        for (auto y : x)
            fout << y << " ";
        fout << "\n";
    }
    return 0;
}