import java.util.*;
public class Main {
public static void main(String args[]) {
Scanner scn=new Scanner(System.in);
int n=scn.nextInt();
int[] array=new int[n];
for(int i=0;i<array.length;i++){
array[i]=scn.nextInt();
}
int m=scn.nextInt();
System.out.print(binarysort(array,m));
}
public static int binarysort(int[] array,int m ){
int lo=0;
int hi=array.length;
for(int i=0;i<array.length;i++){
int mid=(lo+hi)/2;
if(array[mid]==m){
return mid;
}else if(array[mid]<m){
lo=mid+1;
}else{
hi=mid-1;
}
return -1;
}
}
}