Language: C++

#include <bits/stdc++.h>
#define REP(i,n) for (long i=0;i<(n);i++)
#define FOR(i,a,b) for (long i=(a);i<(b);i++)
#define RREP(i,n) for(long i=n;i>=0;i--)
#define RFOR(i,a,b) for(long i=(a);i>(b);i--)
#define dump1d_arr(array) REP(i,array.size()) cerr << #array << "[" << (i) << "] ==> " << (array[i]) << endl;
#define dump2d_arr(array) REP(i,array.size()) REP(j,array[i].size()) cerr << #array << "[" << (i) << "]" << "[" << (j) << "] ==> " << (array[i][j]) << endl;
#define dump(x)  cerr << #x << " => " << (x) << endl;
#define CLR(vec) { REP(i,vec.size()) vec[i] = 0; } 
#define llINF (long long) 9223372036854775807
#define loINF (long) 2147483647
#define shINF (short) 32767
#define SORT(c) sort((c).begin(),(c).end())
#define DEBUG

using namespace std;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef pair<int,int> pr;
typedef ll long long;
typedef vector<ll> Vll;

long N, K;
int t;
short c = 0;
short total = 0;
ll data[100000] = {0};
// memset( data , 0 , sizeof(data) );
Vll ans;

int main(){
    cin >> N;
    REP(i, N){
        cin >> data[i];
    }
    sort(data, data+N);
    for(int i= N-1; i >= 0; i--){
        // // cout << data[i];
        if (data[i] == 0) break;
        if(ans.size() >= 2){
            break;
        }
        if (data[i] == data[i - 1]){
            ans.push_back(data[i]);
            i--;
        }
    }
    if(ans.size() >= 2){
            cout << ans[0] * ans[1];
            return 0;
    }else{
        cout << 0;
        return 0;
    }
}

Compiler output:
a.cc:20:9: error: 'll' does not name a type
   20 | typedef ll long long;
      |         ^~
a.cc:21:16: error: 'll' was not declared in this scope
   21 | typedef vector<ll> Vll;
      |                ^~
a.cc:21:18: error: template argument 1 is invalid
   21 | typedef vector<ll> Vll;
      |                  ^
a.cc:21:18: error: template argument 2 is invalid
a.cc:27:1: error: 'll' does not name a type; did you mean 'Vll'?
   27 | ll data[100000] = {0};
      | ^~
      | Vll
a.cc: In function 'int main()':
a.cc:34:20: error: invalid types '<unresolved overloaded function type>[long int]' for array subscript
   34 |         cin >> data[i];
      |                    ^
a.cc:36:20: error: invalid operands of types '<unresolved overloaded function type>' and 'long int' to binary 'operator+'
   36 |     sort(data, data+N);
      |                ~~~~^~
a.cc:39:17: error: invalid types '<unresolved overloaded function type>[int]' for array subscript
   39 |         if (data[i] == 0) break;
      |                 ^
a.cc:40:16: error: request for member 'size' in 'ans', which is of non-class type 'Vll' {aka 'int'}
   40 |         if(ans.size() >= 2){
      |                ^~~~
a.cc:43:17: error: invalid types '<unresolved overloaded function type>[int]' for array subscript
   43 |         if (data[i] == data[i - 1]){
      |                 ^
a.cc:43:28: error: invalid types '<unresolved overloaded function type>[int]' for array subscript
   43 |         if (data[i] == data[i - 1]){
      |                            ^
a.cc:44:17: error: request for member 'push_back' in 'ans', which is of non-class type 'Vll' {aka 'int'}
   44 |             ans.push_back(data[i]);
      |                 ^~~~~~~~~
a.cc:44:31: error: invalid types '<unresolved overloaded function type>[int]' for array subscript
   44 |             ans.push_back(data[i]);
      |                               ^
a.cc:48:12: error: request for member 'size' in 'ans', which is of non-class type 'Vll' {aka 'int'}
   48 |     if(ans.size() >= 2){
      |            ^~~~
a.cc:49:24: error: invalid types 'Vll {aka int}[int]' for array subscript
   49 |             cout << ans[0] * ans[1];
      |                        ^
a.cc:49:33: error: invalid types 'Vll {aka int}[int]' for array subscript
   49 |             cout << ans[0] * ans[1];
      |                                 ^