Language: C++

#include<iostream>
#include<vector>
using namespace std;

int main(){
    int n,q,d,x;
    vector<int>A;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>q>>d;
        if(q==0){
            cin>>x;
            if(d==0){
                int it=A.begin();
                A.insert(it,x);
            }
            if(d==1){
                A.push_back(x);
            }
        }
        if(q==1){
            cout<<A[d]<<endl;
        }
        if(q==2){
            A.pop_back();
        }
    }
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:14:31: error: cannot convert 'std::vector<int>::iterator' to 'int' in initialization
   14 |                 int it=A.begin();
      |                        ~~~~~~~^~
      |                               |
      |                               std::vector<int>::iterator
a.cc:15:25: error: no matching function for call to 'std::vector<int>::insert(int&, int&)'
   15 |                 A.insert(it,x);
      |                 ~~~~~~~~^~~~~~
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:2:
/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, 2 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:135:27: note:   no known conversion for argument 1 from 'int' to 'std::vector<int>::const_iterator'
  135 |     insert(const_iterator __position, const value_type& __x)
      |            ~~~~~~~~~~~~~~~^~~~~~~~~~
/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:1395:29: note:   no known conversion for argument 1 from 'int' to 'std::vector<int>::const_iterator'
 1395 |       insert(const_iterator __position, value_type&& __x)
      |              ~~~~~~~~~~~~~~~^~~~~~~~~~
/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:1413:29: note:   no known conversion for argument 1 from 'int' to 'std::vector<int>::const_iterator'
 1413 |       insert(const_iterator __position, initializer_list<value_type> __l)
      |              ~~~~~~~~~~~~~~~^~~~~~~~~~
/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, 2 provided