Language: C++

#include <algorithm>
using namespace std;

int main() {
  int N;
  cin >> N;
  vector<long> A(N);
  for (int i =0; i<N; i++) {
    cin >> A.at(i);
  }
  
  vector<long> gcd(N);
  long minGcd = 1000000000; long maxGcd = 0;
  for (int i =0; i<N-1; i++) {
    gcd.at(i) = __gcd(A.at(i),A.at(i+1));
    minGcd = min(gcd.at(i),minGcd);
  }
  vector<int> kouho; //GCDを最小にしてしまう隣り合う2数を取り出す
  bool check = false;
  for (int i =0; i<N-1; i++) {
    if (__gcd(A.at(i),A.at(i+1)) == minGcd && i == N-2) {
      kouho.push_back(i);
      kouho.push_back(i+1);
    } else if (__gcd(A.at(i),A.at(i+1)) == minGcd) {
      kouho.push_back(i);
    }
    if (kouho.size() >= 10) {
      check = true;
      break;
    }
  }
  if (!check) {
    for (int x : kouho) {
      long ansKouho = A.at(0);
      if (x == 0) ansKouho = A.at(1);
      for (int i =0; i<N; i++) {
        if (i == x) continue;
        ansKouho = __gcd(A.at(i),ansKouho);
      }
      maxGcd = max(ansKouho,maxGcd);
    }
    cout << maxGcd << endl;
  } else {
    cout << minGcd << endl;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:3: error: 'cin' was not declared in this scope
    6 |   cin >> N;
      |   ^~~
a.cc:2:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    1 | #include <algorithm>
  +++ |+#include <iostream>
    2 | using namespace std;
a.cc:7:3: error: 'vector' was not declared in this scope
    7 |   vector<long> A(N);
      |   ^~~~~~
a.cc:2:1: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
    1 | #include <algorithm>
  +++ |+#include <vector>
    2 | using namespace std;
a.cc:7:10: error: expected primary-expression before 'long'
    7 |   vector<long> A(N);
      |          ^~~~
a.cc:9:12: error: 'A' was not declared in this scope
    9 |     cin >> A.at(i);
      |            ^
a.cc:12:10: error: expected primary-expression before 'long'
   12 |   vector<long> gcd(N);
      |          ^~~~
a.cc:15:5: error: 'gcd' was not declared in this scope
   15 |     gcd.at(i) = __gcd(A.at(i),A.at(i+1));
      |     ^~~
a.cc:15:23: error: 'A' was not declared in this scope
   15 |     gcd.at(i) = __gcd(A.at(i),A.at(i+1));
      |                       ^
a.cc:18:10: error: expected primary-expression before 'int'
   18 |   vector<int> kouho; //GCDを最小にしてしまう隣り合う2数を取り出す
      |          ^~~
a.cc:21:15: error: 'A' was not declared in this scope
   21 |     if (__gcd(A.at(i),A.at(i+1)) == minGcd && i == N-2) {
      |               ^
a.cc:22:7: error: 'kouho' was not declared in this scope
   22 |       kouho.push_back(i);
      |       ^~~~~
a.cc:25:7: error: 'kouho' was not declared in this scope
   25 |       kouho.push_back(i);
      |       ^~~~~
a.cc:27:9: error: 'kouho' was not declared in this scope
   27 |     if (kouho.size() >= 10) {
      |         ^~~~~
a.cc:33:18: error: 'kouho' was not declared in this scope
   33 |     for (int x : kouho) {
      |                  ^~~~~
a.cc:34:23: error: 'A' was not declared in this scope
   34 |       long ansKouho = A.at(0);
      |                       ^
a.cc:42:5: error: 'cout' was not declared in this scope
   42 |     cout << maxGcd << endl;
      |     ^~~~
a.cc:42:5: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:42:23: error: 'endl' was not declared in this scope
   42 |     cout << maxGcd << endl;
      |                       ^~~~
a.cc:2:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
    1 | #include <algorithm>
  +++ |+#include <ostream>
    2 | using namespace std;
a.cc:44:5: error: 'cout' was not declared in this scope
   44 |     cout << minGcd << endl;
      |     ^~~~
a.cc:44:5: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:44:23: error: 'endl' was not declared in this scope
   44 |     cout << minGcd << endl;
      |                       ^~~~
a.cc:44:23: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'