Language: C++

// Contest: AtCoder Beginner Contest 165 (https://atcoder.jp/contests/abc165)
// Problem: C: Many Requirements (https://atcoder.jp/contests/abc165/tasks/abc165_c)


// region {{{ boilerplate
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <chrono>
#include <cstdint>
#include <deque>
#include <exception>
#include <forward_list>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#if __cplusplus >= 201703L
#   include <optional>
#   include <string_view>
#   include <variant>
#endif

using namespace std;

#if __cplusplus >= 201703L
#   define all(a)      begin(a),end(a)
#   define sz(x)       ((int)size(x))
#else
#   define all(a)      (a).begin(),(a).end()
#   define sz(x)       ((int)(x).size())
#endif

#define rep(a, b)      for(int a = 0; a < (b); ++a)
#define reps(a, b, c)  for(int a = (b); a < (c); ++a)
#define trav(a, b)     for(auto& a : b)

using ll = long long;
using ld = long double;
using u64 = uint64_t;
using u32 = uint32_t;

using pi = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vvi = vector<vi>;
using vpi = vector<pi>;

#if __cplusplus >= 201703L
#   define MAYBE_UNUSED [[maybe_unused]]
#else
#   define MAYBE_UNUSED
#endif

MAYBE_UNUSED static constexpr int INF = (int)1e9 + 5;
MAYBE_UNUSED static constexpr ll INFL = (ll)1e18 + 5;
MAYBE_UNUSED static mt19937 rng((u32)chrono::duration_cast<chrono::nanoseconds>(chrono::high_resolution_clock::now().time_since_epoch()).count());
//endregion }}}

vector<array<int, 4>> t;

int brute(vector<int>& a, int n, int m) {
    if (sz(a) == n) {
        int ai,b,c,d,sum = 0;
        trav(ti, t) {
            tie(ai,b,c,d) = ti;
            if (a[b-1] - a[ai-1] == c)
                sum += d;
        }
        return sum;
    }

    int mn = sz(a) ? a.back() : 1;
    int mx = 0;
    a.push_back(0);
    reps(i, mn, m + 1) {
        a.back() = i;
        mx = max(mx, brute(a, n, m));
    }
    a.pop_back();
    return mx;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m, q; cin >> n >> m >> q;
    t.resize(q);
    for (auto& ti : t)
        cin >> ti[0] >> ti[1] >> ti[2] >> ti[3];
    vi a;
    a.reserve(10);
    cout << brute(a, n, m) << '\n';

    return 0;
}

Compiler output:
a.cc: In function 'int brute(std::vector<int>&, int, int)':
a.cc:87:29: error: no match for 'operator=' (operand types are 'std::tuple<int&, int&, int&, int&>' and 'std::array<int, 4>')
   87 |             tie(ai,b,c,d) = ti;
      |                             ^~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68,
                 from /usr/include/c++/14/bitset:52,
                 from a.cc:8:
/usr/include/c++/14/tuple:1930:9: note: candidate: 'template<class ... _UElements> std::__enable_if_t<((bool)__assignable<const _UElements& ...>()), std::tuple< <template-parameter-1-1> >&> std::tuple< <template-parameter-1-1> >::operator=(const std::tuple<_Args1 ...>&) [with _UElements = {_UElements ...}; _Elements = {int&, int&, int&, int&}]'
 1930 |         operator=(const tuple<_UElements...>& __in)
      |         ^~~~~~~~
/usr/include/c++/14/tuple:1930:9: note:   template argument deduction/substitution failed:
a.cc:87:29: note:   'std::array<int, 4>' is not derived from 'const std::tuple<_UTypes ...>'
   87 |             tie(ai,b,c,d) = ti;
      |                             ^~
/usr/include/c++/14/tuple:1940:9: note: candidate: 'template<class ... _UElements> std::__enable_if_t<((bool)__assignable<_UElements ...>()), std::tuple< <template-parameter-1-1> >&> std::tuple< <template-parameter-1-1> >::operator=(std::tuple<_Args1 ...>&&) [with _UElements = {_UElements ...}; _Elements = {int&, int&, int&, int&}]'
 1940 |         operator=(tuple<_UElements...>&& __in)
      |         ^~~~~~~~
/usr/include/c++/14/tuple:1940:9: note:   template argument deduction/substitution failed:
a.cc:87:29: note:   'std::array<int, 4>' is not derived from 'std::tuple<_UTypes ...>'
   87 |             tie(ai,b,c,d) = ti;
      |                             ^~
/usr/include/c++/14/tuple:1907:7: note: candidate: 'std::tuple< <template-parameter-1-1> >& std::tuple< <template-parameter-1-1> >::operator=(std::__conditional_t<((bool)__assignable<const _Elements& ...>()), const std::tuple< <template-parameter-1-1> >&, const std::__nonesuch&>) [with _Elements = {int&, int&, int&, int&}; std::__conditional_t<((bool)__assignable<const _Elements& ...>()), const std::tuple< <template-parameter-1-1> >&, const std::__nonesuch&> = const std::tuple<int&, int&, int&, int&>&]'
 1907 |       operator=(__conditional_t<__assignable<const _Elements&...>(),
      |       ^~~~~~~~
/usr/include/c++/14/tuple:1909:52: note:   no known conversion for argument 1 from 'std::array<int, 4>' to 'std::__conditional_t<true, const std::tuple<int&, int&, int&, int&>&, const std::__nonesuch&>' {aka 'const std::tuple<int&, int&, int&, int&>&'}
 1907 |       operator=(__conditional_t<__assignable<const _Elements&...>(),
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1908 |                                 const tuple&,
      |                                 ~~~~~~~~~~~~~       
 1909 |                                 const __nonesuch&> __in)
      |                                 ~~~~~~~~~~~~~~~~~~~^~~~
/usr/include/c++/14/tuple:1918:7: note: candidate: 'std::tuple< <template-parameter-1-1> >& std::tuple< <template-parameter-1-1> >::operator=(std::__conditional_t<((bool)__assignable<_Elements ...>()), std::tuple< <template-parameter-1-1> >&&, std::__nonesuch&&>) [with _Elements = {int&, int&, int&, int&}; std::__conditional_t<((bool)__assignable<_Elements ...>()), std::tuple< <template-parameter-1-1> >&&, std::__nonesuch&&> = std::tuple<int&, int&, int&, int&>&&]'
 1918 |       operator=(__conditional_t<__assignable<_Elements...>(),
      |       ^~~~~~~~
/usr/include/c++/14/tuple:1920:47: note:   no known conversion for argument 1 from 'std::array<int, 4>' to 'std::__conditional_t<true, std::tuple<int&, int&, int&, int&>&&, std::__nonesuch&&>' {aka 'std::tuple<int&, int&, int&, int&>&&'}
 1918 |       operator=(__conditional_t<__assignable<_Elements...>(),
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1919 |                                 tuple&&,
      |                                 ~~~~~~~~       
 1920 |                                 __nonesuch&&> __in)
      |                                 ~~~~~~~~~~~~~~^~~~