#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;
    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 foun\n");
    return 0;
}