#include<bits/stdc++.h> using namespace std; long long a[10005],n,key; void halfsearch(){ long long left=1,right=n; while(left<=right){ long long mid=(right+left)/2; if(key==a[mid]){ cout<<mid; return; } else if(key<a[mid]){ right=mid-1; } else{ left=mid+1; } } cout<<"-1"; } int main(){ cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; } cin>>key; halfsearch(); }