#include<bits/stdc++.h>
#define ll long long

using namespace std;

const int N = 6e5 + 100;

struct re{
	ll x, y;
	ll pre, nex;
};
ll n, h = -1;
int sum[N];
re v[N];

void erase_list(ll x){
	if (v[x].pre == 0) h = v[x].nex;
	v[v[x].pre].nex = v[x].nex, v[v[x].nex].pre = v[x].pre;
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	cin >> n;
	int x, cnt = 0;
	for (int i = 1; i <= n; i ++) {
		cin >> x;
		if (i != n){
			v[++ cnt].x = x, v[cnt].y = i, v[cnt].pre = i - 1, v[cnt].nex = i + 1;
			if (i == 1) h = i;
		}else 
			v[++ cnt].x = x, v[cnt].y = i, v[cnt].pre = i - 1, v[cnt].nex = -1;
			
//		cout << i << ":   " << v[cnt].pre << " & " << v[cnt].nex << "\n";
	}
	
	bool b = 0;
	while (cnt){
		ll o = -1, b = 0;
		
		for (ll i = h; i != -1;){
			if (v[i].x != o){
				cnt	--;
				o = v[i].x;
				cout << i << " ";
				erase_list(i);
				b = 1;
//				cout << "////////////////////////////////////////////////////////////\n";
//				for (int j = h; v[j].nex != -1; j = v[j].nex){
//					cout << v[j].y << ":   " << v[j].pre << " & " << v[j].nex << "\n";
//				}
//				cout << "------------------------------------------------------------\n";
			}else i = v[i].nex;
		}
		
		if (b)
		cout << "\n";
	}
	
	return 0;
}

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