Language: C++

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

const ll INF = 1LL << 60;
const ll MOD = ll(1e9)+7;


int main() {
    ll H, W, M;
    cin >> H >> W >> M;

    // vector<vector<ll>> S(H, vector<ll>(W));
    



    // for (ll i = 0; i < H; i++) {
    //     for (ll j = 0; j < W; j++) {
    //         cin >> S.at(i).at(j);
    //     }
    // }

    vector<vector<ll>> S(M, vector<ll>(2));


    vector<vector<ll>> same;

    vector<ll> hnum(H,0);
    vector<ll> wnum(W,0);

    for (ll i = 0; i < M; i++) {
        cin >> S.at(i).at(0) >> S.at(i).at(1);
        hnum.at(S.at(i).at(0)-1)++;
        wnum.at(S.at(i).at(1)-1)++;

        if(S.at(i).at(0) == S.at(i).at(1)) same.push_back(S.at(i).at(j));
    }

    ll hmax = 0;
    ll wmax = 0;
    vector<ll> hmaxindex;
    vector<ll> wmaxindex;
    
    for (ll i = 0; i < H; i++) {
        if(hnum.at(i) >= hmax) {
            hmax = hnum.at(i);
            hmaxindex.push_back(i);
        }
    }

    for (ll i = 0; i < W; i++) {
        if(wnum.at(i) >= wmax) {
            wmax = wnum.at(i);
            wmaxindex.push_back(i);
        }
    }

    ll ans = wmax + hmax;

    for (ll i = 0; i < hmaxindex.size(); i++) {
        for (ll j = 0; j < wmaxindex.size(); j++) {
            
            for (ll k = 0; k < same.size(); k++) {
                if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
            }
            
        }
    }
    
    

    
    cout << ans << endl;
    
    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:37:70: error: 'j' was not declared in this scope
   37 |         if(S.at(i).at(0) == S.at(i).at(1)) same.push_back(S.at(i).at(j));
      |                                                                      ^
a.cc:65:32: error: no match for 'operator==' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} and '__gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type' {aka 'long long int'})
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                     ~~~~~~~~~~ ^~ ~~~~~~~~~~~~~~~
      |                            |                  |
      |                            |                  __gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type {aka long long int}
      |                            __gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type {aka std::vector<long long int>}
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and '__gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type' {aka 'long long int'}
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and '__gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type' {aka 'long long int'}
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
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:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::pair<_T1, _T2>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
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:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/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:
a.cc:65:49: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   65 |                 if (same.at(i) == hmaxindex.at(i) || same.at(i) == hmaxindex.at(j)) ans = ans -1;
      |                                                 ^
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<cla