#include <stdio.h>

int main() 
{
    int n;
    scanf("%d",&n);
    int arr[n];
    for(int i=0;i<n;i++)
    {
    scanf("%d",&arr[i]);
    }
   
    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("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;
}