#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int test(int* arr,int size);

void main()
{

//    int arr[] = {-3,-2,-1,0,1,2,3,3,4,5,6,7,8,9};
//     int arr[] = {0,0,1,2,3,4,5,6,7,8,9,10,11,12};
    int arr[] ={-3,-2,-1,0,1,2,3,4,5,6,7,8,8};



    printf("%d \n",test(arr, 14));

}


int test(int* arr,int size)
{
    int mid,low =0,high = size-1;

    while (low <= high)
    {
        mid = (high + low) / 2;

        if (arr[mid] == arr[mid +1] || arr[mid] == arr[mid -1] )
        {
            return arr[mid];
        }

        if (arr[mid] - arr[0] == mid)
            low = mid +1;
        else
            high = mid -1;

    }


    return -1;
}