#include <iostream>
#include <stack>
#include <vector>

using Operation = std::pair<bool, int>;

int n, idx = 0;
std::stack<int> stack;
std::vector<int> sequence;
std::vector<Operation> operation_log;


int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    std::cin >> n;
    operation_log.reserve(2 * n);
    sequence.resize(n);
    for (int i = 0; i < n; i++) {
        std::cin >> sequence[i];
    }

    for (int current_num = 1; current_num <= n;) {
        while ((stack.empty() || stack.top() != sequence[idx]) && current_num <= n) {
            stack.push(current_num);
            operation_log.emplace_back(false, current_num);
            current_num++;
        }
        while (!stack.empty() && stack.top() == sequence[idx]) {
            stack.pop();
            operation_log.emplace_back(true, sequence[idx]);
            idx++;
        }
    }
    if (!stack.empty()) {
        std::cout << "NO" << std::endl;
    } else {
        for (const auto [op, x] : operation_log) {
            std::cout << (op ? "POP " : "PUSH ") << x << std::endl;
        }
    }


    return 0;
}