Aita

input/code.cpp: In function 'int main()':
input/code.cpp:27:30: error: aggregate 'std::stringstream ss' has incomplete type and cannot be defined
                 stringstream ss;
                              ^

#include <iostream>
#include <stdlib.h>
#include <vector>
#include <algorithm>
#include <string>

using namespace std;

int main() {
    int n, k;
     cin >> n >> k;

    vector<int> aita;
        for (int i = 1; i < n + 1; i+= 2) {
            aita.push_back(i);
        }

        for (int i = 2; i < n + 1; i+= 2) {
            aita.push_back(i);
        }

        if (n != 2) {
                string test ="";
            for (int i = 0; i < n; i++) {
                int a = aita.at(i);
                stringstream ss;
ss << a;
string str = ss.str();
                test = test + str;
        }
        cout << test;
        } else {
           cout << "QAQ";
        }
}