Language: C++

#pragma region macro
#include <bits/stdc++.h>
using i64 = int_fast64_t;
#define repeat(i, a, b) for(int i = (a); (i) < (b); ++(i))
#define rep(i, n) repeat(i, 0, n)

namespace std {
template <typename A, typename B>
string to_string(pair<A, B> p);

string to_string(const string &s) {
    return '"' + s + '"';
}

string to_string(const char *s) {
    return to_string((string)s);
}

string to_string(bool b) {
    return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
    bool first = true;
    string res = "{";
    for(int i = 0; i < static_cast<int>(v.size()); i++) {
        if(!first) {
            res += ", ";
        }
        first = false;
        res += to_string(v[i]);
    }
    res += "}";
    return res;
}

template <size_t N>
string to_string(bitset<N> v) {
    string res = "";
    for(size_t i = 0; i < N; i++) {
        res += static_cast<char>('0' + v[i]);
    }
    return res;
}

template <typename A>
string to_string(A v) {
    bool first = true;
    string res = "{";
    for(const auto &x : v) {
        if(!first) {
            res += ", ";
        }
        first = false;
        res += to_string(x);
    }
    res += "}";
    return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
    return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
};  // namespace std
#pragma endregion

void solve() {
    i64 n, k;
    std::cin >> n >> k;
    std::vector<i64> a(n);
    std::vector<i64> f(n);
    rep(i, n) std::cin >> a[i];
    rep(i, n) std::cin >> f[i];
    std::sort(a.begin(), a.end());
    std::reverse(a.begin(), a.end());
    std::sort(f.begin(), f.end());
    // 二分探索
    i64 ng = 0,
        ok = 1e18;
    while(std::abs(ok - ng) > 1) {
        i64 mid = ng + (ok - ng) / 2;
        i64 cnt = 0;
        rep(i, n) {
            cnt += std::max(a[i] - mid / f[i], 0LL);
        }
        if(cnt <= k) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    std::cout << ok << std::endl;
}

int main() {
    // std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    solve();
    return 0;
}

Compiler output:
a.cc: In function 'void solve()':
a.cc:85:28: error: no matching function for call to 'max(__gnu_cxx::__alloc_traits<std::allocator<long int>, long int>::value_type, long long int)'
   85 |             cnt += std::max(a[i] - mid / f[i], 0LL);
      |                    ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:85:28: note:   deduced conflicting types for parameter 'const _Tp' ('long int' and 'long long int')
   85 |             cnt += std::max(a[i] - mid / f[i], 0LL);
      |                    ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:85:28: note:   mismatched types 'std::initializer_list<_Tp>' and 'long int'
   85 |             cnt += std::max(a[i] - mid / f[i], 0LL);
      |                    ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~