#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;
}