Language: C++

#include <bits/stdc++.h>
#include <algorithm>
#include <vector>
#define rep(i,n) for(int i=0;i<(n);++i)
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)
using namespace std;
typedef long long ll;

int main() {

    int n;
    vector <int> a(200005);
    vector <int> b;
    cin>>n;
    rep(i,n)    cin>>a.at(i);
    int m=n%2;

    rep(i,n) {
        if(i%2==m) {
            b.insert(a[i]);
        }
        else {
            b.pb(a[i]);
        }
    }

    rep(i,n) {
        cout<<b[i]<<endl;
    } 

 return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:21:21: error: no matching function for call to 'std::vector<int>::insert(__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type&)'
   21 |             b.insert(a[i]);
      |             ~~~~~~~~^~~~~~
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_vector.h:1484:9: note: candidate: 'template<class _InputIterator, class> std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with <template-parameter-2-2> = _InputIterator; _Tp = int; _Alloc = std::allocator<int>]'
 1484 |         insert(const_iterator __position, _InputIterator __first,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:1484:9: note:   candidate expects 3 arguments, 1 provided
In file included from /usr/include/c++/14/vector:72:
/usr/include/c++/14/bits/vector.tcc:133:5: note: candidate: 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(const_iterator, const value_type&) [with _Tp = int; _Alloc = std::allocator<int>; iterator = std::vector<int>::iterator; const_iterator = std::vector<int>::const_iterator; value_type = int]'
  133 |     vector<_Tp, _Alloc>::
      |     ^~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/vector.tcc:133:5: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:1395:7: note: candidate: 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(const_iterator, value_type&&) [with _Tp = int; _Alloc = std::allocator<int>; iterator = std::vector<int>::iterator; const_iterator = std::vector<int>::const_iterator; value_type = int]'
 1395 |       insert(const_iterator __position, value_type&& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:1395:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:1413:7: note: candidate: 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(const_iterator, std::initializer_list<_Tp>) [with _Tp = int; _Alloc = std::allocator<int>; iterator = std::vector<int>::iterator; const_iterator = std::vector<int>::const_iterator]'
 1413 |       insert(const_iterator __position, initializer_list<value_type> __l)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:1413:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:1439:7: note: candidate: 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(const_iterator, size_type, const value_type&) [with _Tp = int; _Alloc = std::allocator<int>; iterator = std::vector<int>::iterator; const_iterator = std::vector<int>::const_iterator; size_type = long unsigned int; value_type = int]'
 1439 |       insert(const_iterator __position, size_type __n, const value_type& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:1439:7: note:   candidate expects 3 arguments, 1 provided