binary search

#include <iostream>
#include <math.h>
#include <climits>
using namespace std;
int binarysearch(int arr[], int n, int key)
{

    int mid;
    int s = 0;
    int e = n;
    while (s <= e)
    {
        mid = (s + e) / 2;
    }
    if (arr[mid] == key)
    {
        return mid;
    }
    else if (arr[mid] > key)
    {
        e = mid - 1;
    }
    else
    {
        s = mid + 1;
    }
    return -1;
}
int main()
{
    int n;
    cin >> n;
    int arr[n];
    for (int i = 0; i < n; i++)
    {
        cin >> arr[i];
    }
    int key;
    cin >> key;
    cout << binarysearch(arr, n, key) << endl;

    return 0;
}