Find duplicates under given constraints in C++

Suppose we have a list with 6 different numbers. Only one number is repeated five times. So there are total 10 elements in the array. Find duplicate numbers using only two comparisons. If the list is like [1, 2, 3, 4, 4, 4, 4, 4, 5, 6], so output is 4.

As there are only 10 numbers, then for any type of duplicate numbers, the range of numbers will be placed from index 3 to 5. By checking these indices, we can find the result.

Example

#include<iostream>
using namespace std;
int getDuplicate(int array[]) {
   if (array[3] == array[4])
      return array[3];
   else if (array[4] == array[5])
      return array[4];
   else
      return array[5];
}
int main() {
   int a[] = {1, 2, 3, 4, 4, 4, 4, 4, 5, 6};
   cout << "Duplicate element: " << getDuplicate(a);
}