#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=0,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;
}