Language: C++

#include <iostream>
#include <cmath> 
#include <algorithm>
#include <vector>
#include <functional>
#include <iomanip>
#define int long long
using namespace std;

int n; long long k;
vector<int> a, f;

long long biSearch(long long lt, long long rt);

int main(){
    cin >> n >> k;
    a.resize(n); f.resize(n);
    long long sum = 0;
    for(int i = 0; i < n; i++){
        cin >> a[i];
        sum += a[i];
    }
    if(sum <= k){
        cout << 0 << endl;
        return 0;
    }
    for(int i = 0; i < n; i++) cin >> f[i];
    sort(f.begin(), f.end());
    sort(a.begin(), a.end(), greater<int>());
    
    long long mx = 0;
    for(int i = 0; i < n; i++){
        mx = max(mx, (long long)a[i]*f[i]);
    }

    cout << biSearch(1, mx) << endl;
    return 0;
}

long long biSearch(long long lt, long long rt){
    if(lt == rt) return lt;
    long long ave = (lt + rt) / 2;
    int difSum = 0;
    for(int i = 0; i < n; i++){
        int kunrengo = ave / f[i];
        difSum += max(0, a[i]-kunrengo);
    }
    if(difSum <= k) return biSearch(lt, ave);
    else return biSearch(ave+1, rt);
    
}

Compiler output:
cc1plus: error: '::main' must return 'int'
a.cc: In function 'long long int biSearch(long long int, long long int)':
a.cc:46:22: error: no matching function for call to 'max(int, __gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type)'
   46 |         difSum += max(0, a[i]-kunrengo);
      |                   ~~~^~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/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:46:22: note:   deduced conflicting types for parameter 'const _Tp' ('int' and '__gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type' {aka 'long long int'})
   46 |         difSum += max(0, a[i]-kunrengo);
      |                   ~~~^~~~~~~~~~~~~~~~~~
/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,
                 from a.cc:3:
/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:46:22: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   46 |         difSum += max(0, a[i]-kunrengo);
      |                   ~~~^~~~~~~~~~~~~~~~~~