import java.util.*;
public class Main {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int N = sc.nextInt();
//array declaration
int [] arr = new int[N];
for(int i = 0; i<=arr.length-1; i++)
{
arr[i] = sc.nextInt();
}
int M = sc.nextInt();
int output = Binary(arr, M);
System.out.println(output);
}
public static int Binary(int [] arr, int M)
{
int low = 0;
int high = arr.length-1;
while(low<=high)
{
int mid = (low + high)/2;
if(M>arr[mid])
{
low = mid + 1;
}
else if(M<arr[mid])
{
high = mid-1;
}
else{
return mid;
}
}
return -1;
}
}
pls hlp ASAP