Array max value Program is correct but testcases are coming wrong

#include
using namespace std;
int main() {
int n;
cin>>n;
if (n<0) {
return 0;
}
else {
int a[n];
for(int i=0 ; i<=n; i++) {
cin>>a[i];
}
int max=0;

for(int i=0 ; i<=n; i++) {
if (a[i]>max){
max=a[i];
}
else {
}}
cout<<max;
}

return 0;

}

@Abhishek4799 hey abhishek int max=arr[0]