#include <stdio.h>

int main() {
    int key;
    scanf("%d",&key);
    int low=0,high-n-1,found=0;
    while(low<=high){
        int mid=(low+high)\2;
        if(arr[mid]==key){
            printf("elements found at index %d\n",mid);
            found=1
            break;
        }
        else if(arr[mid]<key){
            low=mid+1;
        }
        else{
            high=mid-1;
        }}
        if(! found)
        printf("element not found\n");
    }
return 0;
}