Language: C++

#include <cstdio> 
#include <ctime> 
#include <cmath>   
#include <cstring>
#include <cstdlib>               //a = clock(); b = clock(); time = a - b;
#include <iostream>                                      
#include <map>                   //map<Type, Type>::iterator it;
#include <queue>                 //priority_queue< Type >Name
#include <stack>                 
#include <vector>                //.push_back()
#include <string>  
#include <algorithm>  
#define e 2.718281828459045      //底数
#define pi 3.141592653589793239  //high precision Π
#define swap(a, b) { int temp = a; a = b; b = temp; }
using namespace std;
typedef long long ll;            //>10^18
typedef long double ld;          //3.3621e-4932 ~ 1.18937e4932
typedef unsigned long long ull;  //>10^20
const int MOD = 1e9 + 7;
const int MAXN = 1e6 + 5;
const int INF = 0x3f3f3f3f;      
const int INFS = 0xc0c0c0c0;     //无穷小
const double eps = 1e-8;         //or 1e-10
//const double pi = acos(-1.0);
inline int read(){
    int sgn = 1, cnt = 0;        //sgn表示正负号 cnt表示读取的数字
    char ch = getchar();
    while(ch < '0' || ch > '9'){ //读取非数字的字符，保留负号，忽略其余无关符号
        if(ch == '-') sgn = -sgn;
        ch = getchar();
    }
    while('0' <= ch && ch <= '9'){
        cnt = cnt * 10 + (ch - '0');
        ch = getchar();
    }
    return sgn * cnt;
}
int main(int argc, char *argv[]){
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);//使用后无法用scanf, printf
	ll a, b, c, d; cin >> a >> b >> c >> d;
	if(a >= 0 && c >= 0) cout << b * d;
	else if(b <= 0 && d <= 0) cout << a * c;
	else cout << max(a * d, b * c, a * c, b * d);
	return 0;
}

Compiler output:
a.cc: In function 'int main(int, char**)':
a.cc:44:25: error: no matching function for call to 'max(ll, ll, ll, ll)'
   44 |         else cout << max(a * d, b * c, a * c, b * d);
      |                      ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/bits/specfun.h:43,
                 from /usr/include/c++/14/cmath:3906,
                 from a.cc:3:
/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:   candidate expects 2 arguments, 4 provided
/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, 4 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:12:
/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, 4 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:   candidate expects 2 arguments, 4 provided