单调栈，cin会超时

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

using namespace std;

int main()
{
    int n;
    vector<int> a, L;
    cin >> n;
    for (int i = 0; i < n; i++) {
        int x;
//         cin >> x;
        scanf("%d", &x);
        a.push_back(x);
    }
    
    stack<int> st;
    for (int i = 0; i < n; i++) {
        while (!st.empty() && a[i] <= a[st.top()]) {
            st.pop();
        }
        
        if (st.empty()) {
            L.push_back(-1);
        } else {
            L.push_back(st.top());
        }   
        st.push(i);
    }
    
    stack<int> st2;
    vector<int> R(n);
    for (int i = n - 1; i >= 0; i--) {
        while (!st2.empty() && a[i] <= a[st2.top()]) {
            st2.pop();
        }
        
        if (st2.empty()) {
            R[i] = -1;
        } else {
            R[i] = st2.top();
        }   
        st2.push(i);
    }
    
    for (int i = 0; i < n; i++) {
//         cout << L[i] << " " << R[i] << endl;
        printf("%d %d\n", L[i], R[i]);
    }
    
    return 0;
}