Binary Search in c++

#include<iostream>
#include<conio.h>
using namespace std;
int main()
{
        int n,num,first=0,middle,last;
        cout<<"Enter the size of your array : ";
        cin>>n;
        int *arr=new int[n];
        cout<<"Enter element of array\n";
        for(int i=0;i<n;i++)
        {
                cin>>arr[i];
        }
        cout<<"\nElement of array\n";
        for(int i=0;i<n;i++)
        {
                cout<<arr[i]<<"\t";
        }
        cout<<"\nEnter number to search : ";
        cin>>num;
        last=n-1;
        middle=(first+last)/2;
        while(first<=last)
        {
                if(arr[middle]<num)
                {
                        first=middle+1;
                }
                else if(arr[middle]==num)
                {
                        cout<<num<<" is found at "<<middle+1<<" possition";
                        break;
                }
                else
                {
                        last=middle-1;
                }
                middle=(first+last)/2;
        }
        if(first>last)
        {
                cout<<num<<" is not found in the array list.";
        }
        getch();
        return 0;
}

Output