Language: C++

#include<bits/stdc++.h>
using namespace std;

int main()
{
  int h, w;
  cin >> h >> w;
  vector<vector<int>> c(h, vector(w));
  int i, j;
  for(i = 0; i < h; i++)
  {
    for(j = 0; j < w; j++)
    {
      cin >> c.at(i).at(j);
    }
  }
  for(i = 0; i < 2 * h; i++)
  {
    for(j = 0; j < w; j++)
    {
      cout << c.at(i/2).at(j)
    }
    cout << endl;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:36: error: class template argument deduction failed:
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
a.cc:8:36: error: no matching function for call to 'vector(int&)'
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:707:9: note: candidate: 'template<class _Tp, class _Alloc, class _InputIterator, class> vector(_InputIterator, _InputIterator, const _Alloc&)-> std::vector<_Tp, _Alloc>'
  707 |         vector(_InputIterator __first, _InputIterator __last,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:707:9: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:678:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::initializer_list<_Tp>, const _Alloc&)-> std::vector<_Tp, _Alloc>'
  678 |       vector(initializer_list<value_type> __l,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:678:7: note:   template argument deduction/substitution failed:
a.cc:8:36: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
/usr/include/c++/14/bits/stl_vector.h:659:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::vector<_Tp, _Alloc>&&, std::__type_identity_t<_Alloc>&)-> std::vector<_Tp, _Alloc>'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:640:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::vector<_Tp, _Alloc>&&, const _Alloc&, std::false_type)-> std::vector<_Tp, _Alloc>'
  640 |       vector(vector&& __rv, const allocator_type& __m, false_type)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note:   candidate expects 3 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:635:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::vector<_Tp, _Alloc>&&, const _Alloc&, std::true_type)-> std::vector<_Tp, _Alloc>'
  635 |       vector(vector&& __rv, const allocator_type& __m, true_type) noexcept
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:635:7: note:   candidate expects 3 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:624:7: note: candidate: 'template<class _Tp, class _Alloc> vector(const std::vector<_Tp, _Alloc>&, std::__type_identity_t<_Alloc>&)-> std::vector<_Tp, _Alloc>'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:624:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:620:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::vector<_Tp, _Alloc>&&)-> std::vector<_Tp, _Alloc>'
  620 |       vector(vector&&) noexcept = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:620:7: note:   template argument deduction/substitution failed:
a.cc:8:36: note:   mismatched types 'std::vector<_Tp, _Alloc>' and 'int'
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
/usr/include/c++/14/bits/stl_vector.h:601:7: note: candidate: 'template<class _Tp, class _Alloc> vector(const std::vector<_Tp, _Alloc>&)-> std::vector<_Tp, _Alloc>'
  601 |       vector(const vector& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:7: note:   template argument deduction/substitution failed:
a.cc:8:36: note:   mismatched types 'const std::vector<_Tp, _Alloc>' and 'int'
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
/usr/include/c++/14/bits/stl_vector.h:569:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::size_t, const _Tp&, const _Alloc&)-> std::vector<_Tp, _Alloc>'
  569 |       vector(size_type __n, const value_type& __value,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:569:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:556:7: note: candidate: 'template<class _Tp, class _Alloc> vector(std::size_t, const _Alloc&)-> std::vector<_Tp, _Alloc>'
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:7: note:   template argument deduction/substitution failed:
a.cc:8:36: note:   couldn't deduce template parameter '_Tp'
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
/usr/include/c++/14/bits/stl_vector.h:542:7: note: candidate: 'template<class _Tp, class _Alloc> vector(const _Alloc&)-> std::vector<_Tp, _Alloc>'
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note:   template argument deduction/substitution failed:
a.cc:8:36: note:   couldn't deduce template parameter '_Tp'
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
/usr/include/c++/14/bits/stl_vector.h:531:7: note: candidate: 'template<class _Tp, class _Alloc> vector()-> std::vector<_Tp, _Alloc>'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:428:11: note: candidate: 'template<class _Tp, class _Alloc> vector(std::vector<_Tp, _Alloc>)-> std::vector<_Tp, _Alloc>'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   template argument deduction/substitution failed:
a.cc:8:36: note:   mismatched types 'std::vector<_Tp, _Alloc>' and 'int'
    8 |   vector<vector<int>> c(h, vector(w));
      |                                    ^
/usr/include/c++/14/bits/stl_vector.h:2033:5: note: candidate: 'template<class _InputIterator, class _ValT, class _Allocator, class, class> std::vector(_InputIterator, _InputIterator, _Allocator)-> vector<_ValT, _Allocator>'
 2033 |     vector(_InputIterator, _InputIterator, _Allocator = _Allocator())
      |     ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:2033:5: note:   candidate expects 2 arguments, 1 provided
a.cc:21:30: error: expected ';' before '}' token
   21 |       cout << c.at(i/2).at(j)
      |                              ^
      |                              ;
   22 |     }
      |     ~