Searching first and last occurrence of key element in O(logn)

/*
Author: Asif Anwar(2019831045)
*/

#include <bits/stdc++.h>

using namespace std;
int main()
{
    int n;
    cout << "Enter the number of elements: ";
    cin >> n;
    int arr[n];
    cout << "Enter the elements: ";
    for(int i=0; i<n; i++) {
        cin >> arr[i];
    }
    int key;
    cout << "Enter the key you want to search: ";
    cin >> key;
    // searching for the first occurrence of the key value
    int begin = 0, end = n-1;
    int upBound = -1, lowBound = -1;
    while(begin<=end){
        int mid = begin + (end-begin)/2;
        if(key==arr[mid]) {
            lowBound = mid;
            end = mid-1;
        }
        else if(key<arr[mid]) {
            end = mid-1;
        }
        else begin = mid+1;
    }
    if(lowBound==-1) cout << "Not found\n";
    else cout << "First occurrence at pos: " << lowBound << "(0 indexed)"<< endl;

    // searching for the last occurrence of the key value
    begin = 0, end = n-1;
    while(begin<=end) {
        int mid = begin + (end-begin)/2;
        if(key==arr[mid]) {
            upBound = mid;
            begin = mid+1;
        }
        else if(arr[mid]>key) {
            end = mid-1;
        }
        else begin = mid+1;
    }
    if(upBound==-1) cout << "Not found\n";
    else cout << "Last occurrence at pos: " << upBound << "(0 indexed)"<< endl;
    return 0;
}