#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");
return 0;
}