#include<cstdio>
#include<vector>
#include<bitset>
using namespace std;
const int nmax = 100005;
int n,m,x,y,i,tsort[nmax],cnt;
vector<int> v[nmax],vt[nmax],s[nmax];
bitset<nmax> viz;
void dfs(int x)
{
    for(vector<int>::iterator it=v[x].begin();it!=v[x].end();it++)
        if(!viz[*it]) {viz[*it]=1; dfs(*it);}
    tsort[++cnt]=x;
}
void dfst(int x)
{
    s[cnt].push_back(x);
    for(vector<int>::iterator it=vt[x].begin();it!=vt[x].end();it++)
        if(!viz[*it]) {viz[*it]=1; dfst(*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].push_back(y);
	    vt[y].push_back(x);
	}
	for(i=1;i<=n;i++) if(!viz[i]) {viz[i]=1; dfs(i);} viz=0; cnt=0;
	for(i=n;i;i--) if(!viz[tsort[i]]) {viz[tsort[i]]=1; cnt++; dfst(tsort[i]);}
	printf("%d\n",cnt);
	for(i=1;i<=cnt;i++,printf("\n")) for(vector<int>::iterator it=s[i].begin();it!=s[i].end();it++) printf("%d ",*it);
	return 0;
}