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

#include<iostream>
#include<cmath>
#include<cstdlib>
#include<string>
#include<cstring>
#include<algorithm>
#include<vector>
#include<map>
#include<iomanip>
#include<set>

using namespace std;

typedef long long ll;

typedef std::pair<int, int> ipair;
bool lessPair(const ipair& l, const ipair& r){return l.second < r.second;}
bool morePair(const ipair& l, const ipair& r){return l.second > r.second;}

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

const ll MOD = 1e9 + 7;
// const long long INF = 1LL<<60;
void add(long long &a, long long b) { a += b; if (a >= MOD) a -= MOD; }
void sub(long long &a, long long b) { a -= b; if (a < 0) a += MOD; }
void mul(long long &a, long long b) { a *= b; a %= MOD; }
ll llmin(ll a, ll b) { if (a < b) return a; else return b; }
ll llmax(ll a, ll b) { if (a < b) return b; else return a; }
ll llabs(ll a) { if (a >= 0) return a; else return - a; }
ll llmodpow(ll a, ll n) {
   if (n == 0) return 1;
   ll tmp = llmodpow(a, n / 2);
   mul(tmp, tmp);
   if (n & 1) mul(tmp, a);
   return tmp;
}

int main() {
   int N;
   cin >> N;
   map<ll, int> log;
   int a;
   for (int i = 0; i < N; i++) {
      cin >> a;
      log[a]++;
   }
   vector<ll> tmp;
   for (auto it = log.begin(); it != log.end(); it++) {
      if (it->second < 2) continue;
      tmp.push_back(it->first);
   }
   if (tmp.size() < 2) cout << 0 << endl;
   sort(tmp.rbegin(), tmp.rend());
   else {
      ll ans = tmp[0] * tmp[1];
      cout << ans << endl;
   }
   return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:67:4: error: 'else' without a previous 'if'
   67 |    else {
      |    ^~~~
Language: C++

#define rep(i,n) repl(i,0,n)
#define sort(a) sort((a).begin(),(a).end())
#define rev(a) reverse((a).begin(),(a).end())
using db = double;
using namespace std;
typedef long long ll;

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i,n) cin >> a[i];
  sort(a);
  rev(a);
  rep(i,n - 3) {
    if (a[i] == a[i+1] == a[i+2] == a[i+3]) {
      cout << a[i] * a[i] << endl;
      return 0;
    }
  }
  int x = 0, y = 0, z;
  rep(i,n - 2) {
    if (a[i] == a[i+1] == a[i+2]) {
      x = a[i];
      z = i+3;
      break;
    } else if (a[i] == a[i+1]) {
      x = a[i];
      z = i+2;
      break;
    }
  }
  repl(i,z,n - 2) {
    if (a[i] == a[i + 1]) {
      y = a[i];
      break;
    }
  }
  cout << x * y << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:3: error: 'cin' was not declared in this scope
   10 |   cin >> n;
      |   ^~~
a.cc:1:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
  +++ |+#include <iostream>
    1 | #define rep(i,n) repl(i,0,n)
a.cc:11:3: error: 'vector' was not declared in this scope
   11 |   vector<int> a(n);
      |   ^~~~~~
a.cc:1:1: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
  +++ |+#include <vector>
    1 | #define rep(i,n) repl(i,0,n)
a.cc:11:10: error: expected primary-expression before 'int'
   11 |   vector<int> a(n);
      |          ^~~
a.cc:12:7: error: 'i' was not declared in this scope
   12 |   rep(i,n) cin >> a[i];
      |       ^
a.cc:1:23: note: in definition of macro 'rep'
    1 | #define rep(i,n) repl(i,0,n)
      |                       ^
a.cc:1:18: error: 'repl' was not declared in this scope; did you mean 'rep'?
    1 | #define rep(i,n) repl(i,0,n)
      |                  ^~~~
a.cc:12:3: note: in expansion of macro 'rep'
   12 |   rep(i,n) cin >> a[i];
      |   ^~~
a.cc:13:8: error: 'a' was not declared in this scope
   13 |   sort(a);
      |        ^
a.cc:2:23: note: in definition of macro 'sort'
    2 | #define sort(a) sort((a).begin(),(a).end())
      |                       ^
a.cc:2:17: error: 'sort' was not declared in this scope
    2 | #define sort(a) sort((a).begin(),(a).end())
      |                 ^~~~
a.cc:13:3: note: in expansion of macro 'sort'
   13 |   sort(a);
      |   ^~~~
a.cc:3:16: error: 'reverse' was not declared in this scope
    3 | #define rev(a) reverse((a).begin(),(a).end())
      |                ^~~~~~~
a.cc:14:3: note: in expansion of macro 'rev'
   14 |   rev(a);
      |   ^~~
a.cc:39:3: error: 'cout' was not declared in this scope
   39 |   cout << x * y << endl;
      |   ^~~~
a.cc:39:3: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:39:20: error: 'endl' was not declared in this scope
   39 |   cout << x * y << endl;
      |                    ^~~~
a.cc:1:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
  +++ |+#include <ostream>
    1 | #define rep(i,n) repl(i,0,n)
Language: Java

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.solve();
    }
    public void solve() {
        Scanner scan = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
        int N = scan.nextInt();
        List<Bar> barlist = new ArrayList<>();
        HashMap<Integer,Bar> bars = new HashMap<>();
        for (int i = 0; i < N; i++) {
            long a = scan.nextLong();
            if (!bars.containsKey(a)) {
                Bar b = new Bar();
                b.x = a;
                b.count = 1;
                barlist.add(b);
                bars.put(a, b);
            } else {
                Bar b = bars.get(a);
                b.count += 1;
            }
        }
        barlist.sort(new BarComparetor());
        long first = 0;
        long second = 0;
        for (int i = 0; i < N && (first == 0 || second == 0); i++) {
            Bar b = barlist.get(i);
            if (b.count == 1) {
                continue;
            }
            if (first == 0) {
                if (4 <= b.count) {
                    first = b.x;
                    second = b.x;
                } else {
                    first = b.x;
                }
                continue;
            }
            if (second == 0) {
                second = b.x;
            }
        }
        System.out.println(first*second);
    }
    class Bar {
        long x;
        int count;
    }
    class BarComparetor implements Comparator<Bar> {
        @Override
        public int compare(Bar o1, Bar o2) {
            if (o1.x== o2.x) {
                return -Integer.compare(o1.count, o2.count);
            }
            return -Long.compare(o1.x, o2.x);
        }
    }
}


Compiler output:
Main.java:22: error: incompatible types: long cannot be converted to Integer
                bars.put(a, b);
                         ^
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error
Language: C++

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

int main() {

 int N;
 cin >> N;

 vector<long long> A(N);
 for(int i = 0;i < N; i++) {
   cin >> A.at(i);
 }

 sort(A.begin(),A.end());
 reverse(A.begin(),A.end());

 int sum = 0,rest = 2,num1 = 0,flag = 0;
 for(int i = 0; i < N - 1;i++) {
   if(A.at(i) == A.at(i + 1)) sum++;
   else sum = 0;

  if(sum == 3)  {
    cout << A.at(i) * A.at(i) << endl;
    break;
  }

  if(flag && sum == 1) {
    cout << num1 * A.at(i) << endl;
    break;
  }
  
  if(sum == 1) {
    num1 = A.at(i);
    flag = 1;
  }

  

  if(i == N - 2) cout << 0 << endl;
 }

Compiler output:
a.cc: In function 'int main()':
a.cc:40:3: error: expected '}' at end of input
   40 |  }
      |   ^
a.cc:4:12: note: to match this '{'
    4 | int main() {
      |            ^
Language: C

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

int asc(const void *a, const void *b) {
  return *(int *)b - *(int *)a;
}

int main(){
  int i,j,k;
  int N;
  scanf("%d",&N);
  
  for(i=0;i<N;i++){
    scanf("%d ",&A[i]);
  }
  int first,second,flgf,flgs;
  flgs=flgf=0;
  qsort(A,sizeof(A) / sizeof(int), sizeof(int), asc);
  
  for(i=0;i<N;i++){
    if(A[i] == A[i+1]){
      if(flgf==0){
        first=A[i];
      }
      if(flgf==1&&flgs==0){
        second=A[i];
      }
    }
    if(flgf == 1 && flgs == 1)
      break;
  }
  
  if(flgs == 0){
    puts("0");
    return 0;
  }
  printf("%ld\n", (long)first * (long)second);
  return 0;
}
      


Compiler output:
main.c: In function 'main':
main.c:14:18: error: 'A' undeclared (first use in this function)
   14 |     scanf("%d ",&A[i]);
      |                  ^
main.c:14:18: note: each undeclared identifier is reported only once for each function it appears in
Language: C

#include<stdio.h>
#include<stblib.h>

int asc(const void *a, const void *b) {
  return *(int *)b - *(int *)a;
}

int main(){
  int i,j,k;
  int N;
  scanf("%d",&N);
  
  for(i=0;i<N;i++){
    scanf("%d ",&A[i]);
  }
  int first,second,flgf,flgs;
  flgs=flgf=0;
  qsort(A,sizeof(A) / sizeof(int), sizeof(int), asc);
  
  for(i=0;i<N;i++){
    if(A[i] == A[i+1]){
      if(flgf==0){
        first=A[i];
      }
      if(flgf==1&&flgs==0){
        second=A[i];
      }
    }
    if(flgf == 1 && flgs == 1)
      break;
  }
  
  if(flgs == 0){
    puts("0");
    return 0;
  }
  printf("%ld\n", (long)first * (long)second);
  return 0;
}
      


Compiler output:
main.c:2:9: fatal error: stblib.h: No such file or directory
    2 | #include<stblib.h>
      |         ^~~~~~~~~~
compilation terminated.
Language: C++

#include<iostream>
#include<algorithm>
#include<vector>

typedef long long ll;

using namespace std;

int main()
{int N ; cin >> N;
 vector<ll> A(N);
 for(int i = 0; i < N; i++){
   cin >> A[i];}
 
 sort(A.begin(),A.end());
 reverse(A.begin(),A.end());
 //Aは降べきの順に並んでいる
 
 int cnt = 0;
 //cnt　が　２未満のときは、長方形が作れないので0出力
 
 int n = 0;
 
 ll B[N];

 
 while( n < N && cnt2 < 2){
   // 小文字nは、今A[n]を調べていることを示している
   int cnt2 = 0 ; ll c = A[n];
   while( n < N && A[n] == c){ cnt2++; //cnt2は、いくつ同じ数字が連続しているかを表す
                              n++;}
       if( cnt2 >= 4 ){ 
         if ( B[0] > c ) {cout << B[0] * c << endl; return 0;}
         else{cout << c * c << endl; return 0;} }
       //一度でも、4種類以上が出たらもう調べなくていい
    else if( 2<= cnt2 && cnt2 < 4){ B[cnt] = c; cnt++;} 
   //もし同じ数字が２つ以上連続していれば、cntを増やし数字記録
 }
 
 if( cnt < 2){ cout << 0 << endl;}
 else{
 ll d = B[0]; ll e = B[1];
   
   cout << d*e << endl;
   
 }
  
 return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:27:18: error: 'cnt2' was not declared in this scope; did you mean 'cnt'?
   27 |  while( n < N && cnt2 < 2){
      |                  ^~~~
      |                  cnt
Language: C++


	long long int hen=0,maxsq=0,t=0,y=0,maxty=0,c=1,ans=0,N,A[100000]={};
	cin>>N;
	for(int i=0;i<N;i++)
	{
		cin>>A[i];
	}
	sort(A,A+N);
	for(int i=0;i<N-1;i++)
	{
		if(A[i]!=A[i+1])c=1;
		if(A[i]==A[i+1])c++;
		if(c==2)
		{
			y=t;
			t=A[i];
		}
		if(c>3)hen=A[i];
	}
	ans=max(y*t,hen*hen);
	cout<<ans;
}

Compiler output:
a.cc:3:9: error: 'cin' does not name a type
    3 |         cin>>N;
      |         ^~~
a.cc:4:9: error: expected unqualified-id before 'for'
    4 |         for(int i=0;i<N;i++)
      |         ^~~
a.cc:4:21: error: 'i' does not name a type
    4 |         for(int i=0;i<N;i++)
      |                     ^
a.cc:4:25: error: 'i' does not name a type
    4 |         for(int i=0;i<N;i++)
      |                         ^
a.cc:8:13: error: expected constructor, destructor, or type conversion before '(' token
    8 |         sort(A,A+N);
      |             ^
a.cc:9:9: error: expected unqualified-id before 'for'
    9 |         for(int i=0;i<N-1;i++)
      |         ^~~
a.cc:9:21: error: 'i' does not name a type
    9 |         for(int i=0;i<N-1;i++)
      |                     ^
a.cc:9:27: error: 'i' does not name a type
    9 |         for(int i=0;i<N-1;i++)
      |                           ^
a.cc:20:9: error: 'ans' does not name a type
   20 |         ans=max(y*t,hen*hen);
      |         ^~~
a.cc:21:9: error: 'cout' does not name a type
   21 |         cout<<ans;
      |         ^~~~
a.cc:22:1: error: expected declaration before '}' token
   22 | }
      | ^
Language: C++

#include <bits/stdc++.h>
#define REP(i,n) for(int i=0;i<n;i++)
long long inf=(long long)1E17;
using namespace std;
int main(){
  int n;
  long long a;
  map<long long,int> mp;
  cin>>n;
  REP(i,n){
    cin>>a;
    mp[a]++;
  }
  vector<int> candidate;
  for(auto p:mp){
    if(p.second<2){
      continue;
    }else if(p.second<4){
      candidate.push_back(p.first);
    }else{
      candidate.push_back(p.first);
      candidate.push_back(p.first);
  }
  
  sort(candidate.begin(),candidate.end());
  reverse(candidate.begin(),candidate.end());
  
  cout<<candidate[0]*candidate[1]<<endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:30:2: error: expected '}' at end of input
   30 | }
      |  ^
a.cc:5:11: note: to match this '{'
    5 | int main(){
      |           ^
Language: C++

import collections

N = int( input() )
A = list( map( int, input().split() ) )

# collections.Counter(a): (aの要素, 出現回数) と組になった Counter オブジェクトを返す
# most_common(): Counter オブジェクトをタプルにして返す
c = collections.Counter(A)
c = c.most_common()
c = sorted( c, reverse=True )  # 要素の大きい順に並び替える

ans = 0
for i,j in c:
    if j >= 4 and ans == 0:
        ans = i*i
        break
    elif j >= 2 and ans == 0:
        ans = i
    elif j >= 2:
        ans *= i
        break

print( ans )

Compiler output:
a.cc:6:3: error: invalid preprocessing directive #collections
    6 | # collections.Counter(a): (aの要素, 出現回数) と組になった Counter オブジェクトを返す
      |   ^~~~~~~~~~~
a.cc:7:3: error: invalid preprocessing directive #most_common
    7 | # most_common(): Counter オブジェクトをタプルにして返す
      |   ^~~~~~~~~~~
a.cc:10:32: error: stray '#' in program
   10 | c = sorted( c, reverse=True )  # 要素の大きい順に並び替える
      |                                ^
a.cc:1:1: error: 'import' does not name a type
    1 | import collections
      | ^~~~~~
a.cc:1:1: note: C++20 'import' only available with '-fmodules-ts'
Language: Java

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;

public class Main {

    public static void main(String[] args) {
        //int N = 10; //; // =
        //int[] sticks = {3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 7,7,7,7,7}; // {3,1,2,4,2,1};
        Scanner sc = new Scanner(System.in);
        N = sc.nextInt();
        int[] sticks = new int[N];
        for (int i=0; i<N; i++){
            sticks[i] = sc.nextInt();
        }

        int area = makeRect(N, sticks);
        System.out.println(area);
    }

    private static int makeRect(int n, int[] sticks) {;
        int area = 0, max1 = 0, max2 = 0, temp = 0;
        if (n < 4)
            System.out.println("insufficient stick");
        else {
            TreeMap<Integer, Integer> stickPair = new TreeMap<>();
            for (int i=0; i<sticks.length; i++){
                if (stickPair.containsKey(sticks[i])){
                    int val = stickPair.get(sticks[i]);
                    stickPair.put(sticks[i], val+1);
                } else
                    stickPair.put(sticks[i], 1);
            }

            for (Map.Entry map : stickPair.entrySet()){
                int val = (int) map.getValue();
                int key = (int) map.getKey();
                if (val >= 4){
                    max1 = max1 > key ? max1 : key;
                    max2 = max2 > key ? max2 : key;
                }
               else if ( val >= 2 && val <=4 ){
                    if (key > max1){
                        temp = max1;
                        max1 = key;
                    }
                    if (max1 > max2){
                        max1 = temp > max2 ? temp : max2;
                        max2 = key;
                    }
                }
            }
            if ((max1 == 0) || (max2 == 0)){
                System.out.println(0);
            }
            area = max1 * max2;
        }
        return area;
    }
}


Compiler output:
Main.java:12: error: cannot find symbol
        N = sc.nextInt();
        ^
  symbol:   variable N
  location: class Main
Main.java:13: error: cannot find symbol
        int[] sticks = new int[N];
                               ^
  symbol:   variable N
  location: class Main
Main.java:14: error: cannot find symbol
        for (int i=0; i<N; i++){
                        ^
  symbol:   variable N
  location: class Main
Main.java:18: error: cannot find symbol
        int area = makeRect(N, sticks);
                            ^
  symbol:   variable N
  location: class Main
4 errors
Language: Java

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;

public class MakeRectangle {

    public static void main(String[] args) {
        //int N = 10; //; // =
        //int[] sticks = {3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 7,7,7,7,7}; // {3,1,2,4,2,1};
        Scanner sc = new Scanner(System.in);
        N = sc.nextInt();
        int[] sticks = new int[N];
        for (int i=0; i<N; i++){
            sticks[i] = sc.nextInt();
        }

        int area = makeRect(N, sticks);
        System.out.println(area);
    }

    private static int makeRect(int n, int[] sticks) {;
        int area = 0, max1 = 0, max2 = 0, temp = 0;
        if (n < 4)
            System.out.println("insufficient stick");
        else {
            TreeMap<Integer, Integer> stickPair = new TreeMap<>();
            for (int i=0; i<sticks.length; i++){
                if (stickPair.containsKey(sticks[i])){
                    int val = stickPair.get(sticks[i]);
                    stickPair.put(sticks[i], val+1);
                } else
                    stickPair.put(sticks[i], 1);
            }

            for (Map.Entry map : stickPair.entrySet()){
                int val = (int) map.getValue();
                int key = (int) map.getKey();
                if (val >= 4){
                    max1 = max1 > key ? max1 : key;
                    max2 = max2 > key ? max2 : key;
                }
               else if ( val >= 2 && val <=4 ){
                    if (key > max1){
                        temp = max1;
                        max1 = key;
                    }
                    if (max1 > max2){
                        max1 = temp > max2 ? temp : max2;
                        max2 = key;
                    }
                }
            }
            if ((max1 == 0) || (max2 == 0)){
                System.out.println(0);
            }
            area = max1 * max2;
        }
        return area;
    }
}


Compiler output:
Main.java:6: error: class MakeRectangle is public, should be declared in a file named MakeRectangle.java
public class MakeRectangle {
       ^
Main.java:12: error: cannot find symbol
        N = sc.nextInt();
        ^
  symbol:   variable N
  location: class MakeRectangle
Main.java:13: error: cannot find symbol
        int[] sticks = new int[N];
                               ^
  symbol:   variable N
  location: class MakeRectangle
Main.java:14: error: cannot find symbol
        for (int i=0; i<N; i++){
                        ^
  symbol:   variable N
  location: class MakeRectangle
Main.java:18: error: cannot find symbol
        int area = makeRect(N, sticks);
                            ^
  symbol:   variable N
  location: class MakeRectangle
5 errors
Language: Java

import java.util.HashMap;
import java.util.Map;

public class Main {

    public static void main(String[] args) {
        int N; // = 10;
        Scanner sc = new Scanner(System.in);
        N = sc.nextInt();
        int[] sticks = new int[N]; // {3, 3, 3, 3, 4, 4, 4, 5, 5, 5}; // {3,1,2,4,2,1};
        for (int i=0; i<N; i++){
            sticks[i] = sc.nextInt();
        }
    }

    private static int makeRect(int n, int[] sticks) {;
        int area = 0, max1 = 0, max2 = 0, temp = 0;
        if (n < 4)
            System.out.println("insufficient stick");
        else {
            HashMap<Integer, Integer> stickPair = new HashMap<>();
            for (int i=0; i<sticks.length; i++){
                if (stickPair.containsKey(sticks[i])){
                    int val = stickPair.get(sticks[i]);
                    stickPair.put(sticks[i], val+1);
                } else
                    stickPair.put(sticks[i], 1);
            }

            for (Map.Entry map : stickPair.entrySet()){
                int val = (int) map.getValue();
                int key = (int) map.getKey();
                if ( val >= 2 ){
                    if (key > max1){
                        temp = max1;
                        max1 = key;
                    }
                    if (max1 > max2){
                        max1 = temp > max2 ? temp : max2;
                        max2 = key;
                    }
                }
            }
            area = max1 * max2;
        }
        return area;
    }
}


Compiler output:
Main.java:8: error: cannot find symbol
        Scanner sc = new Scanner(System.in);
        ^
  symbol:   class Scanner
  location: class Main
Main.java:8: error: cannot find symbol
        Scanner sc = new Scanner(System.in);
                         ^
  symbol:   class Scanner
  location: class Main
2 errors
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main () {
  int N;
  cin >> N;
  vector<int> data(N);
  for(int i = 0; i < N; i++) {
    cin >> data.at(i);
  }
  sort(data.begin(), data.end());
  reverse(data.begin(), data.end());
  int a = -1, b = -1, flag = 0;
  for(int i = 0; i < N - 1; i++) {
    if(data.at(i) == data.at(i + 1) && flag = 0) {
      a = data.at(i);
      flag++;
      i++;
      continue;
    }
    if(data.at(i) == data.at(i + 1) && flag = 1) {
      b = data.at(i);
      break;
    }
    
  }
  if(a == -1 || b == -1) cout << 0 << endl;
  else cout << 2 * (a + b) << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:37: error: lvalue required as left operand of assignment
   14 |     if(data.at(i) == data.at(i + 1) && flag = 0) {
      |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
a.cc:20:37: error: lvalue required as left operand of assignment
   20 |     if(data.at(i) == data.at(i + 1) && flag = 1) {
      |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
Language: C++

#include <stdio.h>
#include <algorithm>
using namespace std;
int main(void){
  int n,a[100000],i=0;
  long x,y;
  scanf("%d",&n);
  for (i=0;i<n;i++) scanf("%d",&a[i]);
  std::sort(a,a+n,std::greater<>());
  while (a[i]!=a[i-1]&&i<n) i++;
  if (i==n){
    printf("0\n");
    return 0;
  }
  x=a[i];
  i+=2;
  while (a[i]!=a[i-1]&&i<n) i++;
  if (i==n){
    printf("0\n");
    return 0;
  }
  y=a[i];
  printf("%ld\n",x*y);
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:24: error: 'greater' is not a member of 'std'
    9 |   std::sort(a,a+n,std::greater<>());
      |                        ^~~~~~~
a.cc:9:32: error: expected primary-expression before '>' token
    9 |   std::sort(a,a+n,std::greater<>());
      |                                ^
a.cc:9:34: error: expected primary-expression before ')' token
    9 |   std::sort(a,a+n,std::greater<>());
      |                                  ^
Language: C++

using namespace std;
#include<bits/stdc++.h>
#define BEGIN ios_base::sync_with_stdio(0);cin.tie(0)
#define END return EXIT_SUCCESS
#define FOR(I,A,B) for((I)=(A);(I)<(B);(I)++)
#define REP(I,N) FOR(I,0,N)
#define UP(I,A,B) for((I)=(A);(I)<=(B);(I)++)
#define DW(I,A,B) for((I)=(A);(I)>=(B);(I)--)
#define IN(P) cin>>(P)
#define IN2(P1,P2) cin>>(P1)>>(P2)
#define IN3(P1,P2,P3) cin>>(P1)>>(P2)>>(P3)
#define INS(I,N,V) REP(I,N) cin>>V[I]
#define INS2(I,N,V1,V2) REP(I,N) cin>>V1[I]>>V2[I];
#define INS3(I,N,V1,V2,V3) REP(I,N) cin>>V1[I]>>V2[I]>>V3[I];
#define OUT(P) cout<<P<<endl
#define OUT2(P1,P2) cout<<P1<<" "<<P2<<endl
#define OUT3(P1,P2,P3) cout<<P1<<" "<<P2<<" "<<P3<<endl
#define OUTS(I,N,V) REP(I,N) cout<<V[i]<<endl
#define ALL(C) (C).begin(),(C).end()
#define RALL(C) (C).rbegin(),(C).rend()
#define mp make_pair
#define pb push_back
typedef unsigned long ul;
typedef unsigned int ui;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
long N,i,B,ans,n;
vector<long> A;
bool use2,use4;

inline void solve(){
  IN(N);
  A.resize(N);
  INS(i,N,A);
  sort(ALL(A));
  REP(i,N){
    n=upper_bound(ALL(A),A[i])-lower_bound(ALL(A),A[i]);
    if(n>=4){
      chmax(ans,A[i]*A[i]);
      B=A[i];
      use4=true;
    }else if(is_second&&n>=2){
      chmax(ans,B*A[i]);
      B=A[i];
    }else if(n>=2){
      if(use4)chmax(ans,B*A[i]);
      B=A[i];
      use2=true;
    }
    i+=n;
  }
  OUT(ans);
}

int main(int argc,char**argv){
  BEGIN;
  solve();
  END;
}


Compiler output:
a.cc: In function 'void solve()':
a.cc:42:14: error: 'is_second' was not declared in this scope
   42 |     }else if(is_second&&n>=2){
      |              ^~~~~~~~~
Language: C++

#include <bits//stdc++.h>
using namespace std;
int in(void){int x;cin>>x;return x;}
#define ll long long int;
#define rep(i,a,b) for(int i=int(a);i<int(b);i++)
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
ll M(int a,int b,int c){
	if(a>=b&&a>=c)return a;
	else if(b>=a&&b>=c)return b;
	else return c;
}
ll m(int a,int b,int c){
	if(a<=b&&a<=c)return a;
	else if(b<=a&&b<=c)return b;
	else return c;
}
/*-----------------------------------------------------*/
int main() {
	int n=in();
	ll f;
	ll l[n];
	rep(i,0,n)cin>>l[i];
	ll t[2]={0},j=0;
	int ch[100000000]={0};
	rep(i,0,n){
		ch[l[i]-1]++;
		if(ch[l[i]-1]==2){
			f=t[0];
			t[0]=M(t[0],t[1],l[i]);
			t[1]=f+t[1]+l[i]-M(f,t[1],l[i])-m(f,t[1],l[i]);
		}
	}
	cout<<t[0]*t[1]<<endl;
	return 0;
}


Compiler output:
a.cc:4:22: error: declaration does not declare anything [-fpermissive]
    4 | #define ll long long int;
      |                      ^~~
a.cc:8:1: note: in expansion of macro 'll'
    8 | ll M(int a,int b,int c){
      | ^~
a.cc:8:4: error: ISO C++ forbids declaration of 'M' with no type [-fpermissive]
    8 | ll M(int a,int b,int c){
      |    ^
a.cc:4:22: error: declaration does not declare anything [-fpermissive]
    4 | #define ll long long int;
      |                      ^~~
a.cc:13:1: note: in expansion of macro 'll'
   13 | ll m(int a,int b,int c){
      | ^~
a.cc:13:4: error: ISO C++ forbids declaration of 'm' with no type [-fpermissive]
   13 | ll m(int a,int b,int c){
      |    ^
a.cc: In function 'int main()':
a.cc:4:22: error: declaration does not declare anything [-fpermissive]
    4 | #define ll long long int;
      |                      ^~~
a.cc:21:9: note: in expansion of macro 'll'
   21 |         ll f;
      |         ^~
a.cc:21:12: error: 'f' was not declared in this scope
   21 |         ll f;
      |            ^
a.cc:4:22: error: declaration does not declare anything [-fpermissive]
    4 | #define ll long long int;
      |                      ^~~
a.cc:22:9: note: in expansion of macro 'll'
   22 |         ll l[n];
      |         ^~
a.cc:22:12: error: 'l' was not declared in this scope
   22 |         ll l[n];
      |            ^
a.cc:4:22: error: declaration does not declare anything [-fpermissive]
    4 | #define ll long long int;
      |                      ^~~
a.cc:24:9: note: in expansion of macro 'll'
   24 |         ll t[2]={0},j=0;
      |         ^~
a.cc:24:12: error: 't' was not declared in this scope
   24 |         ll t[2]={0},j=0;
      |            ^
a.cc:24:21: error: 'j' was not declared in this scope
   24 |         ll t[2]={0},j=0;
      |                     ^
Language: C++

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

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    vector<long long> A;
    for (int i = 0; i < N; i++) {
        int x;
        cin >> x;
        A.push_back(x);
    }
    sort(A.begin(), A.end());
    int shrt = 0, lng = 0;
    for (int i = 0; i < N - 1; i++) {
        if (A[i] == A[i + 1]) {
            i++;
            shrt = lng;
            lng = now;
            if (i + 3 < N) {
                if (A[i] == A[i + 3]) {
                    i++;
                    i++;
                    shrt = lng;
                    lng = now;
                }
            }
        }
    }
    cout << shrt * lng;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:21:19: error: 'now' was not declared in this scope; did you mean 'pow'?
   21 |             lng = now;
      |                   ^~~
      |                   pow
Language: C++

//2018.11.17

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

int main() {
    int n;
    cin >> n;
    vector<int> a;
    int tmp;
    for(int i=0;i<n;i++){
        cin >> tmp;
        a.push_back(tmp);
    }

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

    int len1 = 0;
    int len2 = 0;

    for(int i=1;i<n;i++){
        if(a[i-1]==a[i] && len1==0){len1 = a[i]; i++;}
        else if(a[i-1]==a[i]&& len2==0) {len2 = a[i];}

        if(len1!=0 && len2!=0) break;
    }

    int ans = len1 * len2;
    cout << ans << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:17:5: error: 'sort' was not declared in this scope; did you mean 'short'?
   17 |     sort(a.begin(),a.end(),greater<int>());
      |     ^~~~
      |     short
Language: C++

#include <iostream>
#include <algorithm>
 
void fastin(int &number) {
    bool negative = false;
    int c;
    number = 0;
    c = getchar_unlocked();
    if (c == '-') {
        negative = true;
        c = getchar_unlocked();
    }
    for (; (c > 47 && c < 58); c = getchar_unlocked()) number = number * 10 + c - 48;
    if (negative) number *= -1;
}
 
void fastout(int64_t n) {
    int64_t N = n, rev, count = 0;
    rev = N;
    if (N == 0) { putchar_unlocked('0'); putchar_unlocked('\n'); return ;}
    while ((rev % 10) == 0) { count++; rev /= 10;}
    rev = 0;
    while (N != 0) { rev = (rev<<3) + (rev<<1) + N % 10; N /= 10;}
    while (rev != 0) { putchar_unlocked(rev % 10 + '0'); rev /= 10;}
    while (count--) putchar('0');
}
     
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
        
    int N; fastin(N);
    int A[N];
    for (int i = 0; i < N; ++i) fastin(A[i]);
    sort(A, A + N, std::greater<int>());
     
    int point1 = -1; int point2 = -1;
    int len1, len2;
    for (int i = 0; i < N - 1; ++i) {
    if (A[i] == A[i + 1]){
           point1 = i; len1 = A[i]; break;
        }
    }
    if (point1 < 0){
        fastout(0); return 0;
    }
    for (int i = point1 + 2; i < N - 1; ++i) {
        if (A[i] == A[i + 1]){
            point2 = i; len2 = A[i]; break;
        }
    }
    if (point2 < 0){
        fastout(0); return 0;
    }    
    int64_t ans = 1LL * len1 * len2;
    fastout(ans);
     
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:29:5: error: 'ios_base' has not been declared
   29 |     ios_base::sync_with_stdio(false);
      |     ^~~~~~~~
a.cc:30:5: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
   30 |     cin.tie(NULL);
      |     ^~~
      |     std::cin
In file included from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
Language: C++

#include <iostream>
#include <algorithm>
 
void fastin(int &number) {
    bool negative = false;
    int c;
    number = 0;
    c = getchar_unlocked();
    if (c == '-') {
        negative = true;
        c = getchar_unlocked();
    }
    for (; (c > 47 && c < 58); c = getchar_unlocked()) number = number * 10 + c - 48;
    if (negative) number *= -1;
}
 
void fastout(int64_t n) {
    int64_t N = n, rev, count = 0;
    rev = N;
    if (N == 0) { putchar_unlocked('0'); putchar_unlocked('\n'); return ;}
    while ((rev % 10) == 0) { count++; rev /= 10;}
    rev = 0;
    while (N != 0) { rev = (rev<<3) + (rev<<1) + N % 10; N /= 10;}
    while (rev != 0) { putchar_unlocked(rev % 10 + '0'); rev /= 10;}
    while (count--) putchar('0');
}
     
int main(){        
    int N; fastin(N);
    int A[N];
    for (int i = 0; i < N; ++i) fastin(A[i]);
    sort(A, A + N, greater<int>());
     
    int point1 = -1; int point2 = -1;
    int len1, len2;
    for (int i = 0; i < N - 1; ++i) {
    if (A[i] == A[i + 1]){
           point1 = i; len1 = A[i]; break;
        }
    }
    if (point1 < 0){
        fastout(0); return 0;
    }
    for (int i = point1 + 2; i < N - 1; ++i) {
        if (A[i] == A[i + 1]){
            point2 = i; len2 = A[i]; break;
        }
    }
    if (point2 < 0){
        fastout(0); return 0;
    }    
    int64_t ans = 1LL * len1 * len2;
    fastout(ans);
     
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:32:20: error: 'greater' was not declared in this scope; did you mean 'std::greater'?
   32 |     sort(A, A + N, greater<int>());
      |                    ^~~~~~~
      |                    std::greater
In file included from /usr/include/c++/14/string:49,
                 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_function.h:353:12: note: 'std::greater' declared here
  353 |     struct greater;
      |            ^~~~~~~
a.cc:32:28: error: expected primary-expression before 'int'
   32 |     sort(A, A + N, greater<int>());
      |                            ^~~
a.cc:32:5: error: 'sort' was not declared in this scope; did you mean 'std::sort'?
   32 |     sort(A, A + N, greater<int>());
      |     ^~~~
      |     std::sort
In file included from /usr/include/c++/14/algorithm:86,
                 from a.cc:2:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note: 'std::sort' declared here
  296 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last);
      | ^~~~
Language: C++

#include <iostream>
#include <algorithm>
using namespace std;
 
void fastin(int &number) {
    bool negative = false;
    int c;
    number = 0;
    c = getchar_unlocked();
    if (c == '-') {
        negative = true;
        c = getchar_unlocked();
    }
    for (; (c > 47 && c < 58); c = getchar_unlocked()) number = number * 10 + c - 48;
    if (negative) number *= -1;
}

void fastout(int n) {
    int N = n, rev, count = 0;
    rev = N;
    if (N == 0) { putchar_unlocked('0'); putchar_unlocked('\n'); return ;}
    while ((rev % 10) == 0) { count++; rev /= 10;}
    rev = 0;
    while (N != 0) { rev = (rev<<3) + (rev<<1) + N % 10; N /= 10;}
    while (rev != 0) { putchar_unlocked(rev % 10 + '0'); rev /= 10;}
    while (count--) putchar('0');
}
     
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
        
    int N; fastin(N);
    int A[N];
    for (int i = 0; i < N; ++i) fastin(A[i]);
    sort(A, A + N, greater<int>());
     
    int point1 = -1; int point2 = -1;
    int len1, len2;
    for (int i = 0; i < N - 1; ++i) {
    if (A[i] == A[i + 1]){
           point1 = i; len1 = A[i]; break;
        }
    }
    if (point1 < 0){
        fastout(0); return 0;
    }
    for (int i = point1 + 2; i < N - 1; ++i) {
        if (A[i] == A[i + 1]){
            point2 = i; len2 = A[i]; break;
        }
    }
    if (point2 < 0){
        fastout(0) return 0;
    }    
    int64 ans = 1LL * len1 * len2;
    fastout(ans);
     
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:54:19: error: expected ';' before 'return'
   54 |         fastout(0) return 0;
      |                   ^~~~~~~
      |                   ;
a.cc:56:5: error: 'int64' was not declared in this scope; did you mean 'int64_t'?
   56 |     int64 ans = 1LL * len1 * len2;
      |     ^~~~~
      |     int64_t
a.cc:57:13: error: 'ans' was not declared in this scope; did you mean 'abs'?
   57 |     fastout(ans);
      |             ^~~
      |             abs
Language: C++

#include<bits/stdc++.h>
#include<vector>
using namespace std;
#define llong long long;
#define MAX 100000
int main(){
  int n; cin >> n;
  int a[10001];
  vector<int> b(0);
  for(int i = 0; i < n; i++){
    cin >> a[i];
  }

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

  for(int i = 0; i < n-1; i++){
    if(a[i] == a[i+1]) {
      p.push_back(a[i]);
      i++;
    }


    if(p.size() == 2){
      cout << p[0]*p[1] << endl;
      return 0;
    }
  }


  cout << 0 << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:10: error: request for member 'begin' in 'a', which is of non-class type 'int [10001]'
   14 |   sort(a.begin(), a.end(), greater<int>());
      |          ^~~~~
a.cc:14:21: error: request for member 'end' in 'a', which is of non-class type 'int [10001]'
   14 |   sort(a.begin(), a.end(), greater<int>());
      |                     ^~~
Language: C++

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

int main(){
  int N;
  cin >>N;
  vector<int> a(N);
  for(int i=0;i<N;i++){
    cin >> a.at(i);
  }
  sort(a.begin(),a.end());
  reverse(a.begin(),a.end());
  int count =1;
  int flag =0;
  int b=0,c=0;
  for(int i=;i<N;i++){
    if(a.at(i-1) == a.at(i)){
      count++;
    }
    else count = 1;
    if(count == 2 && flag == 0){
      b = a.at(i);
    }
    if(count == 4){
      c = a.at(i);
      break;
    }
    if(count == 2 && flag == 1){
      c = a.at(i);
      break;
    }
  }
  cout << b*c << endl;
}
    
  

Compiler output:
a.cc: In function 'int main()':
a.cc:16:13: error: expected primary-expression before ';' token
   16 |   for(int i=;i<N;i++){
      |             ^
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,j=0;
    cin>>a;
    long long int b[a],c[a]={0}
    for(int i=0;i<a;i++) cin>>b[i];
    sort(b,b+a);
    reverse(b,b+a);
    for(int i=1;i<a;i=i+2){
        if(b[i]==b[i-1]) {c[j]=b[i]; j++;}
    }
    cout<<c[0]*c[1]<<endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:7:5: error: expected ',' or ';' before 'for'
    7 |     for(int i=0;i<a;i++) cin>>b[i];
      |     ^~~
a.cc:7:17: error: 'i' was not declared in this scope
    7 |     for(int i=0;i<a;i++) cin>>b[i];
      |                 ^
Language: C++

#ABC071C
N=int(input())
A=list(map(int,input().split()))
A_sorted=sorted(A,reverse=True)
long_line=0
lines=1
for i in range(N-1):
    if A_sorted[i]==A_sorted[i+1]:
        lines+=1
    if A_sorted[i]!=A_sorted[i+1] or i==N-2:
        if lines>=4:
            if long_line>0:
                print(long_line*A_sorted[i])
                exit()
            else:
                print(pow(A_sorted[i], 2))
                exit()
        elif lines>=2:
            if long_line>0:
                print(long_line * A_sorted[i])
                exit()
            else:
                long_line=A_sorted[i]
        lines=1
print(0)


Compiler output:
a.cc:1:2: error: invalid preprocessing directive #ABC071C
    1 | #ABC071C
      |  ^~~~~~~
a.cc:2:1: error: 'N' does not name a type
    2 | N=int(input())
      | ^
Language: Java

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.stream.Collectors;

public class MakeARectangle {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		List<Long> bars = new ArrayList<>();
		long h = 0;
		long w = 0;

		for (int i = 0; i < n; i++) {
			long x = Integer.parseInt(sc.next());
			bars.add(x);
		}

		Map<Object, Long> result = bars.stream().collect(
				Collectors.groupingBy(x -> x, Collectors.counting()));

		Object[] uniqueBars = bars.stream()
		.distinct().sorted(Comparator.reverseOrder()).toArray();

		for (Object x : uniqueBars) {
			if (result.get(x) >= 4) {
				h = (long) x;
				w = (long) x;
				break;
			}
			else if (result.get(x) >= 2 && h == 0) {
				h = (long) x;
			} else if (result.get(x) >= 2 && w == 0) {
				w = (long) x;
			}
		}

		System.out.println(h * w);
	}
}


Compiler output:
Main.java:8: error: class MakeARectangle is public, should be declared in a file named MakeARectangle.java
public class MakeARectangle {
       ^
1 error
Language: C++

#include<cstdio>
#include<algorithm>
const int N=1e5+50;
int n,f[N],a,b;
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++)scanf("%d",&f[i]);
    sort(f+1,f+n+1);
    for(int i=n;i>=1;i--){
        if(!a)
        if(f[i]==f[i+1]){
            a=f[i];
            while(f[i]==f[i+1])i--;
        }else if(f[i]==f[i+1]){
            a=f[i];
            while(f[i]==f[i+1])i--;
        }
        if(a&&b)break;
    }
    printf("%lld\n",(long long)a*(long long)b);
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:5: error: 'sort' was not declared in this scope; did you mean 'std::sort'?
    8 |     sort(f+1,f+n+1);
      |     ^~~~
      |     std::sort
In file included from /usr/include/c++/14/algorithm:86,
                 from a.cc:2:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note: 'std::sort' declared here
  296 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last);
      | ^~~~
Language: C++

#include <iostream>
#include<bits/stdc++.h>
using namespace std;
long long int a[5000000];
int main()
{
    long long int i,n,m,j,k=0,l,r;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%lld",&a[i]);
    }
    sort(a+1,a+1+n);
    for(i=n;i>=2;)
    {
        if(a[i]==a[i-1])
        {
            if(k==0)
            {
                l=a[i];
            }else
            {
                r=a[i];
            }
            k++;
            i-=2;
        }else
        {
            i==;
        }
        if(k==2)
        {
            break;
        }
    }
    long long int s=l*r;
    if(k==2)
    {
        printf("%lld",s);
    }else
    {
        printf("0");
    }
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:29:16: error: expected primary-expression before ';' token
   29 |             i==;
      |                ^
Language: C++

#include <iostream>
#include <string>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <map>
#define range(i,a,b) for(auto i=a;i<=b;++i)
#define LL long long
#define itrange(i,a,b) for(auto i=a;i!=b;++i)
#define rerange(i,a,b) for(auto i=a;i>=b;--i)
#define fill(arr,tmp) memset(arr,tmp,sizeof(arr))
using namespace std;
int n;
LL num[int(1e9+5)],ans[2];
bool cmp(int a,int b){
    return a>b;
}
void init(){
    cin>>n;
    range(i,1,n)cin>>num[i];
    sort(num+1,num+1+n,cmp);
}
void solve(){
    int cnt=1,pos=0;
    range(i,2,n){
        if(num[i]==num[i-1])++cnt;
        else cnt=1;
        if(cnt==2||cnt==4)ans[pos++]=num[i];
        if(pos==2)break;
    }
    if(pos<2)cout<<0<<endl;
    else cout<<ans[0]*ans[1]<<endl;
}
int main() {
    init();
    solve();
    return 0;
}

Compiler output:
/tmp/ccSTT53v.o: in function `solve()':
a.cc:(.text+0x153): relocation truncated to fit: R_X86_64_PC32 against symbol `ans' defined in .bss section in /tmp/ccSTT53v.o
a.cc:(.text+0x1a8): relocation truncated to fit: R_X86_64_PC32 against symbol `ans' defined in .bss section in /tmp/ccSTT53v.o
a.cc:(.text+0x1af): relocation truncated to fit: R_X86_64_PC32 against symbol `ans' defined in .bss section in /tmp/ccSTT53v.o
collect2: error: ld returned 1 exit status
Language: C++

#include <iostream>
#include <string>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <map>
#define range(i,a,b) for(auto i=a;i<=b;++i)
#define LL long long
#define itrange(i,a,b) for(auto i=a;i!=b;++i)
#define rerange(i,a,b) for(auto i=a;i>=b;--i)
#define fill(arr,tmp) memset(arr,tmp,sizeof(arr))
using namespace std;
LL n,num[int(1e9+5)],ans[2];
bool cmp(int a,int b){
    return a>b;
}
void init(){
    cin>>n;
    range(i,1,n)cin>>num[i];
    sort(num+1,num+1+n,cmp);
}
void solve(){
    int cnt=1,pos=0;
    range(i,2,n){
        if(num[i]==num[i-1])++cnt;
        else cnt=1;
        if(cnt==2||cnt==4)ans[pos++]=num[i];
        if(pos==2)break;
    }
    if(pos<2)cout<<0<<endl;
    else cout<<ans[0]*ans[1]<<endl;
}
int main() {
    init();
    solve();
    return 0;
}

Compiler output:
/tmp/ccjLO6Z0.o: in function `solve()':
a.cc:(.text+0x159): relocation truncated to fit: R_X86_64_PC32 against symbol `ans' defined in .bss section in /tmp/ccjLO6Z0.o
a.cc:(.text+0x1b5): relocation truncated to fit: R_X86_64_PC32 against symbol `ans' defined in .bss section in /tmp/ccjLO6Z0.o
a.cc:(.text+0x1bc): relocation truncated to fit: R_X86_64_PC32 against symbol `ans' defined in .bss section in /tmp/ccjLO6Z0.o
collect2: error: ld returned 1 exit status
Language: C++

#include <iostream>
#include <cmath>
#include <string>
#include <set>
#include <vector>
#include <map>
#include <list>
#include <stack>
#define lar(a, b) ((a>b) ? (a):(b))
using namespace std;
typedef long long ll;
typedef pair<ll, ll> p;

int main(void) {
    vector<p> cnt;
    p pir;
    pir = make_pair(-1, 0);
    cnt.push_back(pir);
    
    ll n, i, tmp, atmp, ans=1, tmpc=0;
    cin >> n;
    ll a[n];
    for(i=0; i<n; i++)
        cin >> a[i];
    sort(a, a+n);
    
    for(i=0; i<n; i++) {
        tmp=1;
        atmp=a[i];
        while(a[i]==a[i+1]) {
            tmp++;
            i++;
        }
        pir = make_pair(atmp, tmp);
        cnt.push_back(pir);
    }
    
    pir = make_pair(-1, 0);
    cnt.push_back(pir);
    
    for(i=cnt.size()-2; i>=1; i--) {
        if(tmpc==0 && cnt[i].second>=2) {
            ans *= cnt[i].first;
            tmpc++;
            continue;
        }
        if(tmpc==1 && cnt[i].second>=2) {
            ans *= cnt[i].first;
            cout << ans << endl;
            return 0;
        }
    }
    cout << 0 << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:25:5: error: 'sort' was not declared in this scope; did you mean 'sqrt'?
   25 |     sort(a, a+n);
      |     ^~~~
      |     sqrt