#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;
}