#include <bits/stdc++.h>
#define N 100005
#define pb push_back

using namespace std;
vector<int>v[N], g[N], s[N];
int n, m, x, y, cnt, tsort[N], i;
bitset<N>viz;
void df(int nod)
{
    if(viz[nod])
        return;
    viz[nod] = 1;
    for(auto it : v[nod])
        df(it);
    tsort[++cnt] = nod;
}
void dft(int nod)
{
    if(viz[nod])
        return;
    viz[nod] = 1;
    s[cnt].pb(nod);
    for(auto it : g[nod])
        dft(it);
}
int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    scanf("%d%d", &n, &m);
    for(; m; m--)
    {
        scanf("%d%d", &x, &y);
        v[x].pb(y);
        g[y].pb(x);
    }
    for(i = 1; i <= n; i++)
        if(!viz[i])
            df(i);
    viz = cnt = 0;
    for(; n; n--)
        if(!viz[tsort[n]])
        {
            cnt++;
            dft(tsort[n]);
        }
    printf("%d\n", cnt);
    for(i = 1; i <= cnt; i++)
    {
        for(auto it : s[i])
            printf("%d ", it);
        printf("\n");
    }
    return 0;
}