Problem4 solved

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

using namespace std;

class QueryStack {
public:
    QueryStack() {}
    bool empty() { return vals.empty(); }
    void push(int x) {
        vals.push(x);
        int next_max = (maxs.empty()) ? x : max(maxs.top(), x);
        maxs.push(next_max);
    }
    void pop() {
        vals.pop();
        maxs.pop();
    }
    int top() {
        return vals.top();
    }
    int stack_max() {
        if (!empty())
            return maxs.top();
        else
            return -(1 << 30);
    }
private:
    stack<int> vals, maxs;
};

class QueryQueue {
public:
    QueryQueue() { }
    bool empty() { return head.empty() && tail.empty(); }
    void push(int x) { tail.push(x); }
    void pop() {
        if (!head.empty()) head.pop();
        else {
            while (!tail.empty()) {
                int x = tail.top();
                tail.pop();
                head.push(x);
            }
        }
    }
    int queue_max() {
        return max(head.stack_max(), tail.stack_max());
    }
private:
    QueryStack head, tail;
};

void solve(vector<int>& seq) {
    int left = 0, right = 1;
    QueryQueue queue;
    queue.push(seq[left]);
    int n_queries; cin >> n_queries;
    for (int i = 0; i < n_queries; ++i) {
        char type; cin >> type;
        if (type == 'R') {
            queue.push(seq[right++]);
        }
        else {
            queue.pop();
            ++left;
        }
        cout << queue.queue_max() << " ";
    }
}

int main() {
    int sz; cin >> sz;
    vector<int> seq(sz);
    for (auto& el : seq) cin >> el;
    solve(seq);
    return 0;
}