criyle/codenet-compile-errors huggingface dataset:
Language: C++

#include<bits/stdc++.h>
using namespace std;
long long a[100001],n,t1,t2,f=1,t3;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)	cin>>a[i];
	sort(a+1,a+n+1);
	for(int i=n;i>=1;i--)
	{
		if(a[i]==a[i-1]&&f==)
		{
			t2=a[i];
			break;
		}
		if(a[i]==a[i-1]&&f==1)
		{
			t1=a[i];
			i--;
			f=0;
		}
	}
	cout<<max(t1*t2,t3*t3); 
}	


Compiler output:
a.cc: In function 'int main()':
a.cc:11:37: error: expected primary-expression before ')' token
   11 |                 if(a[i]==a[i-1]&&f==)
      |                                     ^
Language: C++

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

int main(){
  int N;
  cin>>N;
  map<ll,int> m;
  vector<ll> cand;
  for(int i=0;i<N;i++){
    ll A;
    cin>>A;
    if(m.count(A)==0){
      m[A]=1;
    }else{
      m[A]++;
    }
    if(m[A]==2){
      m.erase(A);
      cand.push_back(A);
    }
  }
  sort(cand.begin(),cand.end());
  reverse(cand.begin(),cand.end());
  if(cand.size()<2){
    cout<<0<<endl;
  }else{
    cout<<cand.at(0)*cand.at(1)<<endl;
  }

}


Compiler output:
a.cc:5:4: error: expected ';' before 'main'
    5 | int main(){
      |    ^~~~~
      |    ;
Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll = long long; 
using vpii = vector<pair<int, int>>;
#define rep(i, n) for (int i = 0; i < (int)n; i++)
ll inf = 1e10;

ll gcd(ll a, ll b){
  return (b != 0) ? gcd(b, a%b) : a;
}

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];
  sort(a.begin(), a.end());
  ll max1 = 0; ll max2 = 0;
  
  for(int i = n-1; i >= 0; ){
    ll now = a[i];
    if(max1 == 0){
      int cnt = 0;
      while(i >= 0 && now == a[i]){++cnt; --i;}
      if(cnt >= 4){max1 = now; max2 = now; break;}
      else if(cnt >= 2) max1 = now;
    }
    else if(max2 == 0){
      int cnt = 0;
      while(i >= 0 && now == a[i]){++cnt; --i;}
      if(cnt >= 2){ max2 = now; break;}
      
    }
    
  }
  cout <<  << "\n";
}  

Compiler output:
a.cc: In function 'int main()':
a.cc:38:12: error: expected primary-expression before '<<' token
   38 |   cout <<  << "\n";
      |            ^~
Language: C++

#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <string>
#include <sstream>
#include <complex>
#include <vector>
#include <list>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>

#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define pb(a) push_back(a)

typedef long long ll;
using namespace std;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

//const int dy[] = { 0, 0, 1, -1 };
//const int dx[] = { 1, -1, 0, 0 };
const int dx[8] = { 1, 0, -1, 0, 1, -1, -1, 1 };
const int dy[8] = { 0, 1, 0, -1, 1, 1, -1, -1 };
ll gcd(ll a, ll b);
ll lcm(ll x, ll y);

vector<ll> a;
map<ll,ll> m;

int main()
{
	ll x=0, y=0;
	ll n;
	cin >> n;
	
	for (int i = 0; i < n; i++){ 
		ll t;
		cin >> t;
		a.push_back(t);
		m[i] = 0;
	}
	
	for (ll i = 0; i < n; i++){
		m[a[i]] = m[a[i]] + 1;
	}

	for (ll i = m.size()-1; i >= 0; i--) {
		if (m[i] >= 4) {
			x = i;
			y = i;
			cout << x * y << endl;
			return;
		}
		else if (m[i] > 1) {
			x = i;
			m.erase(i);
			break;
		}
	}
	for (ll i = m.size() - 1; i >= 0; i--) {
		if (m[i] > 1) {
			y = i;
			m.erase(i);
			break;
		}
	}

	if (x != 0 && y != 0) {
		cout << x*y << endl;
	}
	else {
		cout << "0" << endl;
	}
	
	
	return 0;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:61:25: error: return-statement with no value, in function returning 'int' [-fpermissive]
   61 |                         return;
      |                         ^~~~~~
Language: C++

# include <cstdio>
# include <algorithm>
using namespace std;

long long a[100005];
int main()
{
    int n;
    scanf("%d",&n);
    long long l = 0 , r = 0;
    for(int i = 1;i <= n;i++)
    {
        scanf("%lld",&a[i]);
    }
    sort(a+1,a+1+n,cmp);
    for(int i = 1;i <= n;i++)
    {
        if(i >= 2 && a[i] == a[i - 1] && a[i] > l) l = a[i];
        if(i >= 4 && a[i] == a[i - 1] && a[i] < l && a[i] > r) r = a[i];
        if(i >= 4 && a[i] == a[i - 1] && a[i] == a[i - 2] && a[i] == a[i - 3] && a[i] > r) r = a[i];
        if(r * l != 0) break;
    }
    printf("%lld",r * l);
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:20: error: 'cmp' was not declared in this scope
   15 |     sort(a+1,a+1+n,cmp);
      |                    ^~~
Language: Java

num = int(input())

arr = {}
for i in input().split(" "):
	i = int(i)
	if arr.get(i, False):
		arr[i] += 1
	else:
		arr[i] = 1

arr = dict(sorted(arr.items(), key=lambda d: d[0], reverse=True))


side = []

for key in arr:
	if arr[key] >= 2:
		side.append(key)

if len(side) >= 2:
	print(side[0] * side[1])
elif len(side) == 1:
	print(side[0] * side[0])
else:
	print(0)


Compiler output:
Main.java:1: error: class, interface, enum, or record expected
num = int(input())
^
1 error
Language: C

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
using namespace std;
int n,a[100100],sum=1,k=0;
int main()
{
    scanf("%d",&n);
    for(int i=1; i<=n; i++)
    {
        scanf("%d",&a[i]);
    }
    sort(a+1,a+1+n);
    for(int i=n; i>=2;)
    {
        if(a[i]==a[i-1])
        {
            sum*=a[i];
            i-=2;
            k++;
          // printf("%d***\n",k);
            if(k==2) break;
        }
        else
            i--;
    }
    if(k<2) printf("0\n");
    else  printf("%d\n",sum);
    return 0;
}


Compiler output:
main.c:3:9: fatal error: iostream: No such file or directory
    3 | #include<iostream>
      |         ^~~~~~~~~~
compilation terminated.
Language: C++

#include <iostream>
#include<algorithm>
using namespace std ;

long long int a[100005] = {0};

int main(){
      int n;
      cin >> n;
      for(int i = 0; i < n; i++){
        cin >> a[i];
      }
      sort(a, a + n);
      long long int x = 0, y = 0;
      for(int  i = n - 1; i >= 0; i--){
        if(a[i] == a[i - 1]){
            ans++;
            if(x == 0){
                x = a[i];
            }else if(y == 0){
                y = a[i];
                break;
            }
            i--;
        }
      }
      cout << x * y << '\n';
}


Compiler output:
a.cc: In function 'int main()':
a.cc:17:13: error: 'ans' was not declared in this scope; did you mean 'abs'?
   17 |             ans++;
      |             ^~~
      |             abs
Language: C++

#include<bits\stdc++.h>
using namespace std;

int n,a;
int main()
{
	while(cin>>n)
	{
		int a1[n+5];
		vector<int> vec;
		set<int> s;
		for(int i=0;i<n;i++)
		{
			cin>>a1[i];
		}
		for(int i=0;i<n;i++)
		{
			if(s.count(a1[i]))
			{
				vec.push_back(a1[i]);
				s.erase(a1[i]);
			}
			else
			s.insert(a1[i]);		
		}
		int size=vec.size(),max=0,max2=0,check=0;
		for(int i=0;i<size;i++)
		{
			if(max<vec[i])
			max=vec[i];
		}
		if(size==0||size==1)
		{
			cout<<"No rectangle can be formed.\n";
			continue;
		}
		for(int i=0;i<size;i++)
		{
			if(max==vec[i])
			check++;
		}
		if(check>=2)
		{
			cout<<max*max<<endl;
		}
		
		else
		{
			for(int i=0;i<size;i++)
			{
				if(max2<vec[i]&&vec[i]!=max)
				max2=vec[i];
			}
			cout<<max2*max<<endl;
		}
		
		
		
	}
















}



Compiler output:
a.cc:1:9: fatal error: bits\stdc++.h: No such file or directory
    1 | #include<bits\stdc++.h>
      |         ^~~~~~~~~~~~~~~
compilation terminated.
Language: C++

from collections import Counter
n=int(input())
a=list(map(int,input().split()))
c=list(Counter(a).items())
c.sort(reverse=True)
ans=0
for a,b in c:
    if(b>=4):
        print(a*a)
        exit()
    elif(b>=2):
        if(ans!=0):
            print(ans*a)
            exit()
        else:
            ans=a
print(0)

Compiler output:
a.cc:1:1: error: 'from' does not name a type
    1 | from collections import Counter
      | ^~~~
Language: C++

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

#define ll long long

int main()
{
  map<ll,ll,greater<ll>> mp;
 int n;
  cin>>n;
  ll arr[n]
  for(int i=0;i<n;i++)
  {
    
    cin>>arr[i];
    mp[arr[i]]++;
    
    
  }
  int flag1=0;
  int flag2=0;
  auto itr=mp.begin();
  for(;itr!=mp.end();itr++)
  {
    if(itr->second>=2)
    {
     	ll len=itr->first;
        flag1=1;
      	itr->second=itr->second-2;
      break;
    }
  }
  for(;itr!=mp.end();itr++)
  {
    if(itr->second>=2)
    {
     	ll breadth=itr->first;
        flag2=1;
      	itr->second=itr->second-2;
      break;
    }
   }
  
  
  if(flag1==0 ||flag2==0)
    cout<<"0"<<endl;
  else
    cout<<len*breadth<<endl;
  
  
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:3: error: expected initializer before 'for'
   12 |   for(int i=0;i<n;i++)
      |   ^~~
a.cc:12:15: error: 'i' was not declared in this scope
   12 |   for(int i=0;i<n;i++)
      |               ^
a.cc:48:11: error: 'len' was not declared in this scope
   48 |     cout<<len*breadth<<endl;
      |           ^~~
a.cc:48:15: error: 'breadth' was not declared in this scope; did you mean 'read'?
   48 |     cout<<len*breadth<<endl;
      |               ^~~~~~~
      |               read
Language: C

#include <stdio.h>
int main() {
    register int arr[10000], i, j, k = 0, n, temp, c[10000], l;
    scanf("%d", &n);
    for (i = 0; i < n; i++)
        scanf("%d", &arr[i]);
    for (i = 0; i < n; i++)
        for (j = 0; j < n -i;j++)
        {
            if(arr[j+1] < arr[j])
            {
                temp = arr[j+1];
                arr[j+1] = arr[j];
                arr[j] = temp;
            }
        }
   for (i = 0; i < n/2; i++)
   { 
       for (j = 0; j < n - 1; j++)
        if (arr[j] == arr[j+1])
        {
            c[k] = arr[j];
            k++;
        }
        l = k;
        k = 0;
   }
   if (l != 0)
    printf("%d", c[l-1] * c[l-2]);
   else
        printf("0");
	return 0;
}

Compiler output:
main.c: In function 'main':
main.c:4:5: error: address of register variable 'n' requested
    4 |     scanf("%d", &n);
      |     ^~~~~
main.c:6:9: error: address of register variable 'arr' requested
    6 |         scanf("%d", &arr[i]);
      |         ^~~~~
main.c:10:13: error: address of register variable 'arr' requested
   10 |             if(arr[j+1] < arr[j])
      |             ^~
main.c:10:13: error: address of register variable 'arr' requested
main.c:12:17: error: address of register variable 'arr' requested
   12 |                 temp = arr[j+1];
      |                 ^~~~
main.c:13:17: error: address of register variable 'arr' requested
   13 |                 arr[j+1] = arr[j];
      |                 ^~~
main.c:13:17: error: address of register variable 'arr' requested
main.c:14:17: error: address of register variable 'arr' requested
   14 |                 arr[j] = temp;
      |                 ^~~
main.c:20:9: error: address of register variable 'arr' requested
   20 |         if (arr[j] == arr[j+1])
      |         ^~
main.c:20:9: error: address of register variable 'arr' requested
main.c:22:13: error: address of register variable 'c' requested
   22 |             c[k] = arr[j];
      |             ^
main.c:22:13: error: address of register variable 'arr' requested
main.c:29:5: error: address of register variable 'c' requested
   29 |     printf("%d", c[l-1] * c[l-2]);
      |     ^~~~~~
main.c:29:5: error: address of register variable 'c' requested
Language: C++

#include<bits/stdc++.h>#define ll long longusing namespace std; bool cmp(ll a, ll b){    return a > b;} int main(){    int n;    while(cin >> n)    {        ll b[n];        map<int,int>a;        for(int i=0; i<n; i++)            cin >> b[i];        sort(b,b+n,cmp);        ll x[3];        int cnt = 0;        int tmp = -1;        for(int i=0; i<n; i++)        {            a[b[i]] ++;            if(a[b[i]] == 2)            {                x[cnt++] = b[i];                tmp = b[i];            }            else if(a[b[i]] == 4 && b[i]==tmp)            {                x[cnt++] = b[i];            }            if(cnt == 2)                break;        }        if(cnt != 2)        {            cout << "0" << endl;            continue;        }        ll ans = x[0]*x[1];        cout << ans << endl;    }    return 0;}

Compiler output:
a.cc:1:24: warning: extra tokens at end of #include directive
    1 | #include<bits/stdc++.h>#define ll long longusing namespace std; bool cmp(ll a, ll b){    return a > b;} int main(){    int n;    while(cin >> n)    {        ll b[n];        map<int,int>a;        for(int i=0; i<n; i++)            cin >> b[i];        sort(b,b+n,cmp);        ll x[3];        int cnt = 0;        int tmp = -1;        for(int i=0; i<n; i++)        {            a[b[i]] ++;            if(a[b[i]] == 2)            {                x[cnt++] = b[i];                tmp = b[i];            }            else if(a[b[i]] == 4 && b[i]==tmp)            {                x[cnt++] = b[i];            }            if(cnt == 2)                break;        }        if(cnt != 2)        {            cout << "0" << endl;            continue;        }        ll ans = x[0]*x[1];        cout << ans << endl;    }    return 0;}
      |                        ^
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/14/../../../x86_64-linux-gnu/Scrt1.o: in function `_start':
(.text+0x17): undefined reference to `main'
collect2: error: ld returned 1 exit status
Language: C++

We have N sticks with negligible thickness. The length of the i-th stick is Ai.
Snuke wants to select four different sticks from these sticks and form a rectangle (including a square), using the sticks as its sides. Find the maximum possible area of the rectangle.

Compiler output:
a.cc:1:1: error: 'We' does not name a type
    1 | We have N sticks with negligible thickness. The length of the i-th stick is Ai.
      | ^~
Language: C

#include<stdio.h>
void main()
{
int t,a[100],n,i,c=0,b=0,j,p=1;
scanf("%d",&n);
for(i=0;i<n;i++)
scanf("%d",&a[i]);
for(i=0;i<n-1;i++)
{
for(j=0;j<n-i-1;j++)
{
if(a[j]>a[j+1])
{ t=a[j];
  a[j]=a[j+1];
  a[j+1]=t;}
}
}
while(p=1)
{
if(a[i]==a[i+1])
{t=i;
c=a[i];
p=0;}
i++
}
for(i=t+1;i<n-1;i++)
{if(a[i]==a[i+1])
{b=a[i];
goto y;}
}
y:
printf("%d",b*c);
}


Compiler output:
main.c: In function 'main':
main.c:24:4: error: expected ';' before '}' token
   24 | i++
      |    ^
      |    ;
   25 | }
      | ~
Language: C

#include<stdio.h>
void main()
{
int t,a[100],n,i,c=0,b=0,j,p;
scanf("%d",&n);
for(i=0;i<n;i++)
scanf("%d",&a[i]);
for(i=0,i<n-1;i++)
{
for(j=0;j<n-i-1;j++)
{
if(a[j]>a[j+1])
{ t=a[j];
  a[j]=a[j+1];
  a[j+1]=t;}
}
}
for(i=0;i<n-1;i++)
{if(a[i]==a[i+1])
{t=i;
c=a[i];
goto x;}}
x:
for(i=t;i<n-1;i++)
{if(a[i]==a[i+1])
{b=a[i];
goto y;}}
y:
printf("%d",b*c);
}




Compiler output:
main.c: In function 'main':
main.c:8:18: error: expected ';' before ')' token
    8 | for(i=0,i<n-1;i++)
      |                  ^
      |                  ;
Language: C++

#include <cstdio>
#include <vector>
using namespace std;

int main()
{
    int n;
    scanf("%d", &n);
    vector<int> a(n);
    for (int i = 0; i < n; i++)
    {
        scanf("%d", &a[i]);
    }

    sort(a.begin(), a.end(), greater<int>());

    int l[2];
    int c = 0;

    for (int i = 1; i < a.size(); i++)
    {
        if (c == 2)
        {
            break;
        }
        if (a[i] == a[i - 1])
        {
            l[c] = a[i];
            c++;
            i++;
        }
    }

    if (c < 2)
    {
        printf("0\n");
    }
    else
    {
        printf("%d\n", l[0] * l[1]);
    }

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:15:5: error: 'sort' was not declared in this scope; did you mean 'short'?
   15 |     sort(a.begin(), a.end(), greater<int>());
      |     ^~~~
      |     short
Language: C++

	/*
	ID: markusz1
	TASK: template
	PROG: template
	LANG: C++
	*/
	#include <bits/stdc++.h>
	using namespace std;
	typedef long long int ll;
	typedef unsigned long long int ul;
	typedef priority_queue<int> p_int_max; // top is max
	typedef priority_queue<int, vector<int>, greater<int> >p_int_min; // top is min
	typedef priority_queue<ll> p_ll;
	typedef priority_queue<double> p_double;
	typedef pair<int, int> pr;
	typedef map<int, int> m_int;
	bool compare_pr_second(pr &a, pr &b){
		if (a.second == b.second) {
			return a.first > b.first;
		} else {
			return a.second > b.second;
		}
	}

	int n,temp;
	ul sum,oof;
	m_int m;
	vector<pr> v;
	int main(){
		ios_base::sync_with_stdio(0);
		cin.tie(0);

		cin >> n;
		for (int i=0;i<n;i++) {
			cin >> temp;
			m[temp]++;
			if (m[temp] == 3) m[temp]=2;
			else if (m[temp] > 4) m[temp]=4;
		}
		for (auto const &item: m) {
			if (item.second >= 2) v.push_back(item);
		}
		sort(v.begin(), v.end(), compare_pr_second);

		//for (auto item: v) cout << item.first << " " << item.second << endl;
		if (!(v[0].second == 2 && v[1].second == 2 || v[0].second == 4)) cout << 0 << endl;
		else {
			for (int i=0; i < v.size(); i++){
				oof = v[i].first*v[i].first;
				// cout << "Big boi" <<  oof << endl;
				if (v[i].second == 4 && sum < oof) {
					sum = oof;
				}
				if (i+1 == v.size() || v[i+1].second < 2) break;
				oof = v[i].first*v[i+1].first
				if (sum < oof) sum = oof;

			}
			cout << sum << endl;
		}
	}


Compiler output:
a.cc: In function 'int main()':
a.cc:55:62: error: expected ';' before 'if'
   55 |                                 oof = v[i].first*v[i+1].first
      |                                                              ^
      |                                                              ;
   56 |                                 if (sum < oof) sum = oof;
      |                                 ~~
Language: C++

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

#define ll long long
#define ull long long unsigned
#define vii vector<int>
#define pii pair<int,int>
#define pll pair<long long,long long>
#define pdd pair<double,double>
#define pldld pair<long long double, long long double>
#define ff first
#define ss second
#define pb push_back
#define read freopen("alu.txt","r",stdin);
#define write freopen("vorta.txt","w",stdout);
#define fastio ios::sync_with_stdio(false); cin.tie(NULL);
#define PI 2*acos(0.0)

const int MAX=100005, MOD=1000000007;
const ll inf=1e9;

int arr[MAX];
vii v;
map<int,int>cnt;
int main(){

    fastio;
    int n;
    cin>>n;
    for(int i=0;i<n;i++){
        int val;
        cin>>val;
        if(!cnt[val]){
            v.pb(val);
        }
        cnt[val]++;
    }
    sort(v.begin(),v.end(),greater<int>());
    int a=0,b=0;
    ll ans=0;
    for(int i=0;i<v.size();i++){
        if(a && b) break;
        if(cnt[v[i]>4){
            ans=v[i]*v[i];
            break;
        }
        if(cnt[v[i]]>1 && !a) a=v[i];
        else if(cnt[v[i]]>1 && !b) b=v[i];
    }
    if(!ans) ans=a*b;
    cout<<ans<<"\n";


}











Compiler output:
a.cc: In function 'int main()':
a.cc:43:22: error: expected ']' before ')' token
   43 |         if(cnt[v[i]>4){
      |                      ^
      |                      ]
Language: C++

#define _USE_MATH_DEFINES
#include "bits/stdc++.h"

using namespace std;
typedef unsigned long long ll;
typedef pair<ll, ll > pi;  
typedef pair<pair<ll, ll >, ll > pii;  
typedef pair<ll, pair<ll, ll > > iip;  
vector<ll > vec;
vector<vector<ll > > vec2;
ll MOD = 1000000007;

int main(){

    ll N;
    cin >> N;

    map<ll, ll > mp;

    for(ll i = 0; i < N; i++){
        ll t = 0; cin >> t;
        mp[t]++;
    }

    priority_queue<pi> que;
    auto begin = mp.begin(), end = mp.end();
    for (auto iter = begin; iter != end; iter++) {
        if(iter -> second >= 2){
            que.push(make_pair(iter->first, iter->second));
        }
    }

    if(que.size() < 2){
        cout << 0 << endl;
    }else{
        if(que.top.second >= 4){
            ll a = que.top().first; que.pop();
            cout << a * a << endl;
        }else{
            ll a = que.top().first; que.pop();
            ll b = que.top().first; que.pop();
            cout << a * b << endl;
        }
    }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:36:16: error: invalid use of member function 'std::priority_queue<_Tp, _Sequence, _Compare>::const_reference std::priority_queue<_Tp, _Sequence, _Compare>::top() const [with _Tp = std::pair<long long unsigned int, long long unsigned int>; _Sequence = std::vector<std::pair<long long unsigned int, long long unsigned int>, std::allocator<std::pair<long long unsigned int, long long unsigned int> > >; _Compare = std::less<std::pair<long long unsigned int, long long unsigned int> >; const_reference = const std::pair<long long unsigned int, long long unsigned int>&]' (did you forget the '()' ?)
   36 |         if(que.top.second >= 4){
      |            ~~~~^~~
      |                   ()
a.cc:36:20: error: expected ')' before 'second'
   36 |         if(que.top.second >= 4){
      |           ~        ^~~~~~
      |                    )
Language: C++

#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstring>
#include<bitset>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<cstdio>
#include<numeric>
#include<set>
#include<math.h>
#include<unordered_map>
using namespace std;

const int dx[4]={1,0,-1,0};
const int dy[4]={0,1,0,-1};

#define rep(i,x) for(int i=0;i<x;i++)
#define re(i,x,y) for(int i=x;i<y;i++)

long long INF=1e9;
const int mod=10007;
#define ll long long

int main(){
    cin>>n;
    vector<ll>a(n);
    rep(i,n){
        cin>>a[i];
    }
    sort(a.begin(),a.end());
    reverse(a.begin(),a.end());
    ll tmp=a[0],ans=1,num1=0;
    for(int i=0;i<n;){
        ll num=0;
        tmp=a[i];
        while(a[i]==tmp){
            num++;
            i++;
        }
        if(num>=4&&num1==0){
            ans*=(tmp*tmp);
            break;
        }else if(num>=4&&num1==1){
            ans*=tmp;
            break;
        }else if(num>=2&&num1<=1){
            ans*=tmp;
            num1++;
            if(num1==2)break;
        }
        if(i==n-1){
            ans=0;
        }
        i++;
    }
    cout<<ans<<endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:29:10: error: 'n' was not declared in this scope; did you mean 'yn'?
   29 |     cin>>n;
      |          ^
      |          yn
Language: C++

#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstring>
#include<bitset>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<cstdio>
#include<numeric>
#include<set>
#include<math.h>
#include<unordered_map>
using namespace std;

const int dx[4]={1,0,-1,0};
const int dy[4]={0,1,0,-1};

#define rep(i,x) for(int i=0;i<x;i++)
#define re(i,x,y) for(int i=x;i<y;i++)

long long INF=1e9;
const int mod=10007;
#define ll long long

int main(){
    cin>>n;
    vector<ll>a(n);
    rep(i,n){
        cin>>a[i];
    }
    sort(a.begin(),a.end());
    reverse(a.begin(),a.end());
    ll tmp=a[0],ans=1,num1=0;
    for(int i=0;i<n;){
        ll num=0;
        tmp=a[i];
        while(a[i]==tmp){
            num++;
            i++;
        }
        if(num>=4&&num1==0){
            ans*=(tmp*tmp);
            break;
        }else if(num>=4&&num1==1){
            ans*=tmp;
            break;
        }else if(num>=2&&num1<=1){
            ans*=tmp;
            num1++;
            if(num1==2)break;
        }
        if(i==n-1&&num1<=1){
            ans=0;
        }
        i++;
    }
    cout<<ans<<endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:29:10: error: 'n' was not declared in this scope; did you mean 'yn'?
   29 |     cin>>n;
      |          ^
      |          yn
Language: C++

#include <bits/stdc++.h>
using namespace std;
int n,a[100000],num;
long long ans+1;
int main(){
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>a[i];
  }
  sort(a,a+n);
  for(int i=n-1;i;i--){
    if(a[i]==a[i-1]){
      ans*=a[i];
      i--;
      num++;
    }
    if(num==2){
      cout<<ans;
      return 0;
    }
  }
  cout<<0;
  return 0;
}

Compiler output:
a.cc:4:14: error: expected initializer before '+' token
    4 | long long ans+1;
      |              ^
a.cc: In function 'int main()':
a.cc:13:7: error: 'ans' was not declared in this scope; did you mean 'abs'?
   13 |       ans*=a[i];
      |       ^~~
      |       abs
a.cc:18:13: error: 'ans' was not declared in this scope; did you mean 'abs'?
   18 |       cout<<ans;
      |             ^~~
      |             abs
Language: C++

#include<iostream>
#include<cmath>
#include<algorithm>
#include<bits/stdc++.h>
using namespace std;
#define ll long longz

int a[1000000]={0};
int main(){
    int n;
    cin >>n;
    map<ll , ll,greater<ll> >mp;
    int b[n];
    for(int i=0;i<n;i++){
        ll k=0;
        cin >>k;
        ll num = mp[k];
        mp[k]=num+1;
    }
    //cout<<mp.size()<<"jj"<<endl;
    ll sum=1;
    ll flag=0,hhh=0;
    for(auto it=mp.begin();it!=mp.end();it++)
    {
        if(flag==2)
            break;
        if(it->second>=2){
            sum*=it->first;
            hhh=1;
            flag++;
        }
    }
    if(hhh)cout<<sum<<endl;
    else cout<<0<<endl;

}


Compiler output:
a.cc: In function 'int main()':
a.cc:12:29: error: wrong number of template arguments (1, should be at least 2)
   12 |     map<ll , ll,greater<ll> >mp;
      |                             ^
In file included from /usr/include/c++/14/map:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152,
                 from a.cc:4:
/usr/include/c++/14/bits/stl_map.h:102:11: note: provided for 'template<class _Key, class _Tp, class _Compare, class _Alloc> class std::map'
  102 |     class map
      |           ^~~
a.cc:15:12: error: expected initializer before 'k'
   15 |         ll k=0;
      |            ^
a.cc:16:15: error: 'k' was not declared in this scope
   16 |         cin >>k;
      |               ^
a.cc:17:12: error: expected initializer before 'num'
   17 |         ll num = mp[k];
      |            ^~~
a.cc:18:15: error: 'num' was not declared in this scope; did you mean 'enum'?
   18 |         mp[k]=num+1;
      |               ^~~
      |               enum
a.cc:21:8: error: expected initializer before 'sum'
   21 |     ll sum=1;
      |        ^~~
a.cc:22:8: error: expected initializer before 'flag'
   22 |     ll flag=0,hhh=0;
      |        ^~~~
a.cc:23:20: error: request for member 'begin' in 'mp', which is of non-class type 'int'
   23 |     for(auto it=mp.begin();it!=mp.end();it++)
      |                    ^~~~~
a.cc:23:35: error: request for member 'end' in 'mp', which is of non-class type 'int'
   23 |     for(auto it=mp.begin();it!=mp.end();it++)
      |                                   ^~~
a.cc:25:12: error: 'flag' was not declared in this scope
   25 |         if(flag==2)
      |            ^~~~
a.cc:28:13: error: 'sum' was not declared in this scope
   28 |             sum*=it->first;
      |             ^~~
a.cc:29:13: error: 'hhh' was not declared in this scope
   29 |             hhh=1;
      |             ^~~
a.cc:30:13: error: 'flag' was not declared in this scope
   30 |             flag++;
      |             ^~~~
a.cc:33:8: error: 'hhh' was not declared in this scope
   33 |     if(hhh)cout<<sum<<endl;
      |        ^~~
a.cc:33:18: error: 'sum' was not declared in this scope
   33 |     if(hhh)cout<<sum<<endl;
      |                  ^~~
Language: C

//ABC071C
#include <bits/stdc++.h>
#include <iostream>
#include <iomanip>
#include <numeric>
#include <math.h>
#include <stdio.h>
#include <climits>
#include <cfloat>
#include <string>
using namespace std;

int main(){
	long long int n;
	cin >> n;
	vector<long long int> a(n);
	for(int i=0;i<n;i++){
		cin >> a.at(i);
	}
	sort(a.begin(),a.end());
	vector<long long int> l(n);
	int i = n-1;
	int j = 0;
	while(i>0){
		if(a.at(i) ==  a.at(i-1)){
			l.at(j) = a.at(i);
			j++;
			i -= 2;
		}else{
			i--;
		}
		if(j == 2){
			long long int s = l.at(0)*l.at(1);
			cout << s << endl;
			return 0;
		}
	}
	cout << "0" << endl;
	return 0;
}


Compiler output:
main.c:2:10: fatal error: bits/stdc++.h: No such file or directory
    2 | #include <bits/stdc++.h>
      |          ^~~~~~~~~~~~~~~
compilation terminated.
Language: C++

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

typedef long long ll

int main(){
    int N;
    cin>>N;
    vector<ll>a;
    for(int i=0;i<N;i++){
        ll t;
        cin>>t;
        a.push_back(t);
    }
    sort(a.begin(), a.end());
    ll max1=0,max2=0;
    for(int i=1;i<N;i++){
        if(a[i-1]==a[i]){
            max2=max1;
            max1=a[i];
            i++;
        }
    }
    cout<<max1*max2<<endl;
    return 0;
}


Compiler output:
a.cc:6:1: error: expected initializer before 'int'
    6 | int main(){
      | ^~~
Language: C++

N = int(input())
A = [int(a) for a in input().split()]
A.sort(reverse=True)
cout = 0
for i in range(1, len(A)):
    if A[i] == A[i - 1]:
        cout = i
        break
for i in range(cout + 2, len(A)):
    if A[i] == A[i - 1]:
        print(A[cout] * A[i])
        break


Compiler output:
a.cc:1:1: error: 'N' does not name a type
    1 | N = int(input())
      | ^
Language: C++

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

using ll = long long;

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

    int n; cin >> n;
    map<int, int> mp;
    for (int i = 0; i < n; ++i) {
        int a; cin >> a;
        mp[a]++;
    }

    ll s1 = 1, s2 = 1;
    for (auto itr = mp.rbegin(); itr != mp.rend(); ++itr) {
        int c1 = 0, c2 = 0;
        if (itr->second >= 4 && c <= 1) {
            s1 = itr->first * itr->first;
            c1++;
        } else if (itr->second >= 2 && c <= 2) {
            s2 *= itr->first;
            c2++;
        }
    }

    cout << ((s1 == 1 && s2 == 1) ? 0 : max(s1, s2)) << endl;

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:20:33: error: 'c' was not declared in this scope; did you mean 'c2'?
   20 |         if (itr->second >= 4 && c <= 1) {
      |                                 ^
      |                                 c2
Language: Java

import java.util.*;
public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();
      int[] a = new int[];
      for(int i = 0;i < n;i++)a[i]=sc.nextInt();
      Arrays.sort(a);
      long x = 1;
      List<Integer> list = new ArrayList<Integer>();
      for(int i = n-1;i > 0;i--){
      	if(a[i]==a[i-1]&&list.size()<=1){
          x *= (long)a[i];
          list.add(a[i]);
          i--;
        }
        if(list.size()==2)break;
      }
      if(list.size()<=1)System.out.println(0);
      else System.out.println(x);
    }
}

Compiler output:
Main.java:6: error: array dimension missing
      int[] a = new int[];
                         ^
1 error
Language: C++

#include <iostream>
#include <map>
#include <vector>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <cstring>
#define rep(i, N) for (int i = 0; i < (int)N; i++)
#define ARRAY_LEN(array) (sizeof(array) / sizeof(array[0]))
using namespace std;
typedef long long ll;
const ll LLINF = 9223372036854775807;
const int INTINF = 2147483647;
const int MOD = 1000000007;

int main() {
  int N; cin >> N;
  ll A[N]; rep(i, N) cin >> A[i];

  map<ll, ll> A_dict;
  rep(i, N) A_dict[A[i]]++;

  vector<ll> bars;
  for(auto x: A_dict) rep(i, x.second/2) bars.push_back(x.first);
  sort(bars.begin(), bars.end()); reverse(bars.begin(), bars.end());

  ll result = 0;
  if (bars.size() >= 2) result = bars[0] * bars[1];
  cout << ll << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:29:14: error: expected primary-expression before '<<' token
   29 |   cout << ll << endl;
      |              ^~
Language: C++

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <list>
#include <queue>
#include <deque>
#include <algorithm>
#include <numeric>
#include <utility>
#include <complex>
#include <functional>
using namespace std;
const int MOD = 1000000007;
typedef int long long;
typedef long long ll;
typedef pair<ll, ll> p;
const int INF = (1 << 28);
const int dx[4] = {0, 1, 0, -1}, dy[4] = {-1, 0, 1, 0};
const int Dx[8] = {0, 1, 1, 1, 0, -1, -1, -1}, Dy[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
#define yes cout << "Yes" << endl
#define YES cout << "YES" << endl
#define no cout << "No" << endl
#define NO cout << "NO" << endl
#define REP(i, n) for (int i = 0; i < n; i++)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define INF 2e9
#define ALL(v) v.begin(), v.end()
int n;
int a[100000];
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n ;
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    sort(a,a+n);

    ll ans=0;
    vector<int> l;
    int c=0;
    for(int i=n-1;i>=1;i--){
        if(l.size()==2)break;
        if(a[i-1]==a[i]&&c-i!=1){
            l.push_back(a[i]);
            c=i;
        }
    }
    if(l.size()==2)
    cout << ll(l[0]*l[1]) << "\n";
    else{
         cout << 0 << "\n";
    }
}

Compiler output:
a.cc:21:18: error: declaration does not declare anything [-fpermissive]
   21 | typedef int long long;
      |                  ^~~~
Language: C++

#include "bits/stdc++.h"
using namespace std;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define repf(i, x, n) for (int i = (int)(x); i < (int)(n); i++)
#define repfr(i, x, n) for (int i = (int)(x)-1; i >= (int)(n); i--)
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}
#define INF 1e9
using ll = int64_t;
#define waru 1000000007

std::int64_t gcd(std::int64_t a, std::int64_t b) {
  // a >= b && b != 0
  std::int64_t c;
  do {
    c = a % b;
    a = b;
    b = c;
  } while (c);

  return a;
}
std::int64_t gcd_s(std::int64_t aa, std::int64_t bb) {
  std::int64_t a = max(aa, bb);
  std::int64_t b = min(aa, bb);
  std::int64_t c;
  if (b == 0) {
    return -1;
  }
  do {
    c = a % b;
    a = b;
    b = c;
  } while (c);

  return a;
}
void rle(std::vector<std::pair<char, std::int64_t>> &data, std::string str) {
  char now = str[0];
  std::int64_t count = 0;
  for (std::int64_t i = 0; i < str.size() + 1; i++) {
    if (i == str.size()) {
      data.push_back(make_pair(str[i - 1], count));
      break;
    } else if (now != str[i]) {
      data.push_back(make_pair(now, count));
      now = str[i];
      count = 0;
    }
    count++;
  }

  return;
}

std::map<ll, ll> m;
void Main() {
  //自動整形防止用コメント
  ll n;
  std::cin >> n;
  std::vector<ll> a(n);
  for (auto &x : a) {
    std::cin >> x;
  }

  //同じ長さの棒が２本以上あること
  //その中で最大の長さの棒を取ること
  priority_queue<ll> q;
  for (auto &x : a) {
    q.push(x);
  }

  ll an[2];
  ll index = 0;
  while (!q.empty()) {
    ll tmp = q.top();
    q.pop();

    if (tmp == q.top() && !q.empty) {
      an[index] = tmp;
      q.pop();
      index++;
      if (index == 2) {
        std::cout << an[0] * an[1] << '\n';
        return;
      }
    }
  }

  std::cout << 0 << '\n';

  return;
}

int main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(15);
  Main();
  return 0;
}


Compiler output:
a.cc: In function 'void Main()':
a.cc:95:30: error: cannot convert 'std::priority_queue<long int>::empty' from type 'bool (std::priority_queue<long int>::)() const' to type 'bool'
   95 |     if (tmp == q.top() && !q.empty) {
      |                              ^~~~~
a.cc:95:30: error: in argument to unary !
   95 |     if (tmp == q.top() && !q.empty) {
      |                            ~~^~~~~
Language: C++

#include <iostream>
#include <cstdio>
#include <map>
using namespace std;
map<int>m;
int n, first, second;
int main()
{
	scanf("%d", &n);
	for(int i = 0; i < n; ++ i)
	{
		int x;
		scanf("%d", &x);
		++ m[x];
		if(m[x] >= 2)
		{
			m[x] -= 2;
			if(x > first)
			{
				second = first;
				first = x;
			}
			else
			second = x;
		}
	}
	printf("%d", first * second);
}

Compiler output:
a.cc:5:8: error: wrong number of template arguments (1, should be at least 2)
    5 | map<int>m;
      |        ^
In file included from /usr/include/c++/14/map:63,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_map.h:102:11: note: provided for 'template<class _Key, class _Tp, class _Compare, class _Alloc> class std::map'
  102 |     class map
      |           ^~~
a.cc: In function 'int main()':
a.cc:14:21: error: invalid types 'int[int]' for array subscript
   14 |                 ++ m[x];
      |                     ^
a.cc:15:21: error: invalid types 'int[int]' for array subscript
   15 |                 if(m[x] >= 2)
      |                     ^
a.cc:17:26: error: invalid types 'int[int]' for array subscript
   17 |                         m[x] -= 2;
      |                          ^
Language: C++

#include <bits/stdc++.h>
#include <ctime>
#include <cstdlib>
#define rep(i, N) for (long i = 0; i < (N); i++)
#define swap(a, b) (a += b, b = a - b, a -= b)
using namespace std;
int main()
{
    int N;
    cin >> N;
    vector<long long> a(N), b(2);
    rep(i, N)
    {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    reverse(a.begin(), a.end());
    b[0] = 0;
    b[1] = 0;
    long long i = 0, j = 1, count = 0, k = 0;
    while (j <= N && k < 2)
    {
        if (a[i] == a[j])
        {
            count++;
            j++;
        }
        else
        {
            if (count >= 2 && count < 4)
            {
                b[k] = a[i];
                k++;
            }
            else if(count >= 4)
            {
                count << a[i] * a[i] << endl;
                return 0;
            }
            count = 1;
            i = j;
            j = i + 1;
        }
    }
    cout << b[0] * b[1] << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:37:38: error: invalid operands of types 'long long int' and '<unresolved overloaded function type>' to binary 'operator<<'
   37 |                 count << a[i] * a[i] << endl;
      |                 ~~~~~~~~~~~~~~~~~~~~~^~~~~~~
Language: C++

#include <bits/stdc++.h>
#include <ctime>
#include <cstdlib>
#define rep(i, N) for (long i = 0; i < (N); i++)
#define swap(a, b) (a += b, b = a - b, a -= b)
using namespace std;
int main()
{
    int N;
    cin >> N;
    vector<long long> a(N), b(2);
    rep(i, N)
    {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    reverse(a.begin(), a.end());
    b[0] = 0;
    b[1] = 0;
    long long i = 0, j = 1, count = 0, k = 0;
    while (j <= N && k < 2)
    {
        if (a[i] == a[j])
        {
            count++;
            j++;
        }
        else
        {
            if (count >= 2 && count < 4)
            {
                b[k] = a[i];
                k++;
            }
            elseif(count >= 4)
            {
                count << a[i] * a[i] << endl;
                return 0;
            }
            count = 1;
            i = j;
            j = i + 1;
        }
    }
    cout << b[0] * b[1] << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:35:13: error: 'elseif' was not declared in this scope
   35 |             elseif(count >= 4)
      |             ^~~~~~
Language: C++

#include<bits/stdc++.h>
#define itn int
#define REP(i,n) for(int i=0;i<(n);i++)
#define IREP(i,n) for(int i=n-1;i>=0;i--)
#define FOR(i,k,n) for(int i=(k);i<(n);i++)
#define REPEACH(itr,k) for(auto&& itr : k)
#define MOD 1000000007

using namespace std;
typedef long long ll;

const ll INF = 1LL<<60;
typedef pair<double,int> P;


int main(){
	int n;
	cin >> n;
	map<int> m;
	vector<ll> v;
	REP(i,n){
		int a;
		cin >> a;
		v.push_back(a);
		m[a]++;
	}
	sort(v.begin(),v.end(),greater<int>());
	int tmp=0;
	int ans=1;
	REP(i,n){
		if(m[v[i]]>1){
			tmp++;
			ans*=v[i];
		}
		if(tmp==2){
			break;
		}
	}
}



Compiler output:
a.cc: In function 'int main()':
a.cc:19:16: error: wrong number of template arguments (1, should be at least 2)
   19 |         map<int> m;
      |                ^
In file included from /usr/include/c++/14/map:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_map.h:102:11: note: provided for 'template<class _Key, class _Tp, class _Compare, class _Alloc> class std::map'
  102 |     class map
      |           ^~~
a.cc:25:18: error: invalid types 'int[int]' for array subscript
   25 |                 m[a]++;
      |                  ^
a.cc:31:21: error: invalid types 'int[__gnu_cxx::__alloc_traits<std::allocator<long long int>, long long int>::value_type {aka long long int}]' for array subscript
   31 |                 if(m[v[i]]>1){
      |                     ^
Language: C++

#include<bits/stdc++.h>
#define itn int
#define REP(i,n) for(int i=0;i<(n);i++)
#define IREP(i,n) for(int i=n-1;i>=0;i--)
#define FOR(i,k,n) for(int i=(k);i<(n);i++)
#define REPEACH(itr,k) for(auto&& itr : k)
#define MOD 1000000007

using namespace std;
typedef long long ll;

const ll INF = 1LL<<60;
typedef pair<double,int> P;


int main(){
	int n;
	cin >> n;
	map<int> m;
	vector<ll> v;
	REP(i,n){
		int a;
		cin >> a;
		v.push_back(a);
		map[a]++;
	}
	sort(v.begin(),v.end(),greater<int>());
	int tmp=0;
	int ans=1;
	REP(i,n){
		if(map[v[i]]>1){
			tmp++;
			ans*=v[i];
		}
		if(tmp==2){
			break;
		}
	}
}



Compiler output:
a.cc: In function 'int main()':
a.cc:19:16: error: wrong number of template arguments (1, should be at least 2)
   19 |         map<int> m;
      |                ^
In file included from /usr/include/c++/14/map:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_map.h:102:11: note: provided for 'template<class _Key, class _Tp, class _Compare, class _Alloc> class std::map'
  102 |     class map
      |           ^~~
a.cc:25:21: error: conflicting declaration 'auto a'
   25 |                 map[a]++;
      |                     ^
a.cc:22:21: note: previous declaration as 'int a'
   22 |                 int a;
      |                     ^
a.cc:25:23: error: expected initializer before '++' token
   25 |                 map[a]++;
      |                       ^~
a.cc:31:23: error: expected unqualified-id before '[' token
   31 |                 if(map[v[i]]>1){
      |                       ^
Language: C

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>

typedef long long int ll;

int MAX(int a, int b){return a>b?a:b;}
int MIN(int a, int b){return a>b?b:a;}
int compare(const void* a, const void* b){return *(int*)a - *(int*)b;}
ll compare(const void* a, const void* b){return *(ll*)a - *(ll*)b;}
ll llMAX(ll a, ll b){return a>b?a:b;}
ll llMIN(ll a, ll b){return a>b?b:a;}
ll digits(ll a){ll tmp=a; ll cnt=0; while(tmp>0){tmp/=10; cnt+=1;} return cnt;}

int main(void){
    int n;
    scanf("%d", &n);
    ll a[n];
    for(int i=0; i<n; i++){scanf("%lld", &a[i]);}
  
    qsort(a, n, sizeof(int), compare);

    int b_idx = 0;
    ll b[n];//本数が2本以上4本未満の長さ(長方形用)
    int c_idx = 0;
    ll c[n];//本数が4本以上の長さ(正方形用)
    for(int i=0; i<n; i++){b[i]=0; c[i]=0;}

    int cnt = 0;
    ll tmp = a[n-1];
    for(int i=n-1; i>=0; i--){
        if(tmp == a[i]){
            cnt += 1;
        }else{
            if(cnt > 3){
                c[c_idx] = tmp;
                c_idx +=1 ;
            }else if(cnt > 1){
                b[b_idx] = tmp;
                b_idx += 1;
            }
            tmp = a[i];
            cnt = 1;
        }
    }

    if(cnt > 3){
        c[c_idx] = tmp;
        c_idx += 1;

    }
    else if(cnt > 1){
        b[b_idx] = tmp;
        b_idx += 1;
    }

    ll ans = 0;

    for(int i=0; i<c_idx; i++){
        ans = llMAX(c[i]*c[i], ans);
    }

    for(int i=0; i<b_idx; i++){
        ans = llMAX(b[i]*b[i+1], ans);
    }

    printf("%lld\n", ans);

    return 0;
}


Compiler output:
main.c:11:4: error: conflicting types for 'compare'; have 'll(const void *, const void *)' {aka 'long long int(const void *, const void *)'}
   11 | ll compare(const void* a, const void* b){return *(ll*)a - *(ll*)b;}
      |    ^~~~~~~
main.c:10:5: note: previous definition of 'compare' with type 'int(const void *, const void *)'
   10 | int compare(const void* a, const void* b){return *(int*)a - *(int*)b;}
      |     ^~~~~~~
main.c: In function 'main':
main.c:22:30: error: passing argument 4 of 'qsort' from incompatible pointer type [-Wincompatible-pointer-types]
   22 |     qsort(a, n, sizeof(int), compare);
      |                              ^~~~~~~
      |                              |
      |                              ll (*)(const void *, const void *) {aka long long int (*)(const void *, const void *)}
In file included from main.c:2:
/usr/include/stdlib.h:971:34: note: expected '__compar_fn_t' {aka 'int (*)(const void *, const void *)'} but argument is of type 'll (*)(const void *, const void *)' {aka 'long long int (*)(const void *, const void *)'}
  971 |                    __compar_fn_t __compar) __nonnull ((1, 4));
      |                    ~~~~~~~~~~~~~~^~~~~~~~
Language: C++

#include <bits/stdc++.h>
using namespace std;
long long a[10000001], k=1, l, r, x;
int main ()
{
    int n, maxn=0;
    cin>>n;
    
    for(int i=0;i<n;i++)
    {
        cin>>x;
        a[x]++;
        maxn=max(maxn,x);
    }
    
    for(int i=maxn;i>=0;i--){
        if(a[i]>=2&&k==1) l=i,k++;
        else if(a[i]>=2&&k==2) r=i;
    }
    cout<<l*r<<endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:17: error: no matching function for call to 'max(int&, long long int&)'
   13 |         maxn=max(maxn,x);
      |              ~~~^~~~~~~~
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: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:13:17: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'long long int')
   13 |         maxn=max(maxn,x);
      |              ~~~^~~~~~~~
/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:13:17: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   13 |         maxn=max(maxn,x);
      |              ~~~^~~~~~~~