#include<bits/stdc++.h>
using namespace std;
int n,s,cnt=1;
set<int>s0,s1;
vector<int>ans[200005];
inline void readint(int &x){
	x=0;
	short flag=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-') flag=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=(x<<3)+(x<<1)+(c^48);
		c=getchar();
	}
	x*=flag;
}
inline void writeint(int x){
	if(x<0){
		putchar('-');
		x=-x;
	}
	if(x>9) writeint(x/10);
	putchar(x%10+'0');
}
int main(){
	readint(n);
	for(int i=1;i<=n;i++){
		readint(s);
		if(s==1) s0.insert(s);
		else s1.insert(s);
	}
	while(!s0.empty()||!s1.empty()){
		int a=*s0.begin();
		int b=*s1.begin();
		if(a<b){
			a=remove(s0,a);
			ans[cnt].push_back(a);
			a=remove(s1,a);
			ans[cnt].push_back(a);
		}else{
			b=remove(s0,b);
			ans[cnt].push_back(b);
			a=remove(s1,b);
			ans[cnt].push_back(b);
		}
	}
	while(!s0.empty()){
		cnt++;
		ans[cnt].push_back(*s1.begin());
		s1.erase();
	}
	while(!s1.empty()){
		cnt++;
		ans[cnt].push_back(*s1.begin());
		s1.erase();
	}
	for(int i=1;i<=cnt;i++){
		while(!ans[cnt].empty()){
			cout<<ans[cnt].front()<<" ";
		}
		cout<<endl;
	}
	return 0;
}//set 编译错误