#include<bits/stdc++.h>
using namespace std;
int main(){
//lets do it
int n;
cin>>n;
int arr[n];
for(int i=0;i<n;i++) cin>>arr[i];
int target;
cin>>target; // target=?
int l=0,h=n-1;
int index=-1;
while(l<=h)
{
int mid=(l+h)/2;
if(arr[mid]==target){
index=mid;
break;
}else if(arr[mid]<target) l=mid+1;
else h=mid-1;
}
cout<<"NUMBER FOUND AT INDEX-"<<index<<endl;
return 0;
}