First and last occurance binary search

#include<vector>
using namespace std;
int firstOcc(vector<int>& arr, int n, int key) {

    int s = 0, e = n-1;
    int mid = s + (e-s)/2;
    int ans = -1;
    while(s<=e) {

        if(arr[mid] == key){
            ans = mid;
            e = mid - 1;
        }
        else if(key > arr[mid]) {//Right me jao
            s = mid + 1;
        }
        else if(key < arr[mid]) {//left me jao
            e = mid - 1;
        }

        mid = s + (e-s)/2;
    }
    return ans;
}

int lastOcc(vector<int>& arr, int n, int key) {

    int s = 0, e = n-1;
    int mid = s + (e-s)/2;
    int ans = -1;
    while(s<=e) {

        if(arr[mid] == key){
            ans = mid;
            s = mid + 1;
        }
        else if(key > arr[mid]) {//Right me jao
            s = mid + 1;
        }
        else if(key < arr[mid]) {//left me jao
            e = mid - 1;
        }

        mid = s + (e-s)/2;
    }
    return ans;
}

pair<int, int> firstAndLastPosition(vector<int>& arr, int n, int k)
{
    pair<int,int> p;
    p.first = firstOcc(arr, n, k);
    p.second = lastOcc(arr, n, k);
    
    return p;
}