#include <iostream>
#include <list>
#include <vector>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> fruits(n);
    for (int i = 0; i < n; ++i) {
        cin >> fruits[i];
    }

    list<pair<int, int>> blocks;  // Pair of (start_index, fruit_type)
    int start = 0;
    
    // Construct initial blocks
    for (int i = 1; i <= n; ++i) {
        if (i == n || fruits[i] != fruits[i - 1]) {
            blocks.emplace_back(start, fruits[start]);
            start = i;
        }
    }

    while (!blocks.empty()) {
        vector<int> basket;
        list<pair<int, int>>::iterator it = blocks.begin();
        int prev_type = -1;

        while (it != blocks.end()) {
            if (it->second != prev_type) {
                basket.push_back(it->first + 1); // Store 1-based index
                ++(it->first);
                prev_type = it->second;
            }

            if (it->first == n || fruits[it->first] != it->second) {
                it = blocks.erase(it);
            } else {
                ++it;
            }
        }

        for (const int& index : basket) {
            cout << index << " ";
        }
        cout << endl;
    }

    return 0;
}