Бинарный поиск в упорядоченном по возрастанию массиве

#include <iostream>
using namespace std;
 
int main()
{
    const int size = 10;
    int arr[size];
    for (int i(0); i < size; ++i)
        arr[i] = i;
    
    int aver = 0;
    int first = 0; 
    int last = size - 1;
    int value;
    cout << "\ninput search value\n"; 
    cin >> value;
                          
    if (last<0) cout << "\nis empty" << endl; 
 
    while (first < last)
    {
        aver = (first + (last - first)) / 2; 
        value <= arr[aver] ? last = aver : first = aver + 1;    
    }
    if (arr[last] == value)
        cout <<"\n"<< last << endl;
    else
        cout << "\nvalue is not found" << endl;
    
    return 0;
}

aver = (first +  last) / 2;

#include <iostream>
 
int BinSearch(int arr[], int size, int key);
 
int main()
{
    const int size {10};
    int arr[size] {2, 34, 45, 67, 98, 110, 115, 200, 349, 555};
    int key;
 
    std::cout << "\nHere is our array: \n\n";
    for (int i = 0; i < size; ++i)
        std::cout << "index [" << i << "] = " << arr [i] << "\n";
 
    std::cout << "\nEnter the key to find: ";
    std::cin >> key;
    if (BinSearch (arr, size, key) == -1)
        std::cout << "\nThere is not such a key in this array\n";
    else
        std::cout << "\nThe key " << key << " has index " << "["
              << BinSearch(arr, size, key) << "]\n";
 
    return 0;
}
 
int BinSearch(int arr [], int size, int key)
{
    int left = 0;
    int right = size - 1;
 
    while (left <= right)
    {
        int mid = (left + right) /2;
        if (arr [mid] == key)
            return mid;
        if (arr [mid] < key)
            left = mid + 1;
        if (arr [mid] > key)
            right = mid - 1;
    }
    return -1;
}