Language: C++

#include <bits/stdc++.h>
#define ALL(a)  (a).begin(),(a).end()
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

int gcd(int a, int b){
  if(a < b) swap(a,b);
  if(b == 0) return a;
  return gcd(b, a % b);
}

//i番目までの最大公約数
int leftgcd(ll i, vector<ll> A, vector<ll> &L){
  if(L.at(i) != -1) return L.at(i);
  return L.at(i) = gcd(leftgcd(i - 1, A, L), A.at(i));
}

//i番目以降の最大公約数
int rightgcd(ll i, vector<ll> A, vector<ll> &R){
  if(R.at(i) != -1) return R.at(i);
  return R.at(i) = gcd(rightgcd(i + 1, A, R), A.at(i));
}

int main(){
  ll N;
  cin >> N;
  vector<ll> A(N+1);
  for(int i = 1; i <= N; i++){
    cin >> A.at(i);
  }
  
  vector<ll> L(N+2, -1);
  L.at(0) = 0;
  L.at(1) = A.at(1);

  vector<ll> R(N+2, -1);
  R.at(N) = A.at(N); 
  R.at(N+1) = 0;

  ll result = 1;
  for(int i = 1; i <= N; i++){
    result = max(result, gcd(leftgcd(i-1, A, L), rightgcd(i+1, A, R)));
  }
  
  cout << result << endl;

}

Compiler output:
a.cc: In function 'int main()':
a.cc:44:17: error: no matching function for call to 'max(ll&, int)'
   44 |     result = max(result, gcd(leftgcd(i-1, A, L), rightgcd(i+1, A, R)));
      |              ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:44:17: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   44 |     result = max(result, gcd(leftgcd(i-1, A, L), rightgcd(i+1, A, R)));
      |              ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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:44:17: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   44 |     result = max(result, gcd(leftgcd(i-1, A, L), rightgcd(i+1, A, R)));
      |              ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~