#include <stdio.h>

int main() {
     int n,key;
     scanf("%d",&n);
     int arr[n];
     for(int i=0;i<n;i++)
         scanf("%d",&arr[i]);
         scanf("%d",&key);
         int low=0,high=n-1,found=0;
     while(low<=high){
         int mid=(low+high)/2;
         if(arr[mid]==key){
             printf("Element 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;
}