#include <bits/stdc++.h>

using namespace std;

int n, m, p, post[100005];
vector<int> v[100005], vt[100005], r;
vector< vector<int> > sol;
bool ok[100005];

void df(int x)
{
    ok[x] = 1;
    for (vector<int>::iterator it = v[x].begin(); it != v[x].end(); ++it)
        if(!ok[*it]){
            ok[*it] = 1;
            df(*it);
        }
    post[++p] = x;
}

void dft(int x)
{
    r.push_back(x);
    ok[x] = 0;
    for (vector<int>::iterator it = vt[x].begin(); it != vt[x].end(); ++it)
        if(ok[*it]){
            ok[*it] = 0;
            dft(*it);
        }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    scanf("%d%d", &n, &m);
    while(m--){
        int x, y;
        scanf("%d%d", &x, &y);
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for (int i = 1; i <= n; ++i)
        if(!ok[i])
            df(i);
    for (int i = p; i >= 1; --i)
        if(ok[post[i]]){
            r.clear();
            dft(post[i]);
            sol.push_back(r);
        }
    printf("%d\n", (int)sol.size());
    for (vector< vector<int> >::iterator it = sol.begin(); it != sol.end(); ++it){
        for (vector<int>::iterator it2 = it->begin(); it2 != it->end(); ++it2)
            printf("%d ", (int)(*it2));
        printf("\n");
    }
    return 0;
}