Language: C++

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) (v).begin(),(v).end()
#define out(a) cout << (a) << endl
using namespace std;
using ll = long long;

int gcd(int a, int b){
    if(a < b) return gcd(b, a);
    int r;
    while ((r = a % b)){
        a = b;
        b = r;
    }
    return b;
}

int main(){
    int k;
    cin >> k;
    vector<vector<int>> vec;
    for(int i=0; i<k; i++) {
        for(int j=0; j<3; j++){
            vec[i][j] == i+1;
        }
    }
    int sum=0;
        
    for(int i=0; i<k; i++){
        for(int j=0; j<k; j++){
            for(int l=0; l<k; l++){
                sum += gcd(gcd(vec[i], vec[j]), vec[l]);
            }
        }
    }

    // do{
    //     rep(i, 3) cout << vec[0] << endl;
    // } while (next_permutation(all(vec)));

    out(sum);
}

Compiler output:
a.cc: In function 'int main()':
a.cc:32:21: error: no match for 'operator+=' (operand types are 'int' and 'std::common_type_t<std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> > >' {aka 'std::vector<int>'})
   32 |                 sum += gcd(gcd(vec[i], vec[j]), vec[l]);
      |                 ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:58,
                 from a.cc:1:
/usr/include/c++/14/numeric: In instantiation of 'constexpr std::common_type_t<_Mn, _Nn> std::gcd(_Mn, _Nn) [with _Mn = vector<int>; _Nn = vector<int>; common_type_t<_Mn, _Nn> = vector<int>]':
a.cc:32:31:   required from here
   32 |                 sum += gcd(gcd(vec[i], vec[j]), vec[l]);
      |                            ~~~^~~~~~~~~~~~~~~~
/usr/include/c++/14/numeric:175:21: error: static assertion failed: std::gcd arguments must be integers
  175 |       static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
      |                     ^~~~~~~~~~~~~~~~~~
/usr/include/c++/14/numeric:175:21: note: 'std::is_integral_v<std::vector<int> >' evaluates to false
/usr/include/c++/14/numeric:177:28: error: no match for 'operator==' (operand types are 'std::vector<int>' and 'int')
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::pair<_T1, _T2>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::move_iterator<_IteratorL>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::move_iterator<_IteratorL>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
In file included from /usr/include/c++/14/bits/char_traits.h:42,
                 from /usr/include/c++/14/string:42,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::fpos<_StateT>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const allocator<_CharT>&, const allocator<_T2>&)'
  235 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:235:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::allocator<_CharT>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:629:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  629 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:629:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/string_view:637:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  637 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:637:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/string_view:644:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  644 |     operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:644:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/bits/basic_string.h:3755:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3755 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3755:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/bits/basic_string.h:3772:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3772 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3772:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   'std::vector<int>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
/usr/include/c++/14/bits/basic_string.h:3819:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3819 |     operator==(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3819:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/numeric:177:28: note:   mismatched types 'const _CharT*' and 'std::vector<int>'
  177 |       static_assert(_Mn(2) == 2 && _Nn(2) == 2,
      |                     ~~~~~~~^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2558:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator==(const tuple<_UTypes .