import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;

public class Solution {

public static void main(String[] args) {
    Scanner scan=new Scanner(System.in);
    int n=scan.nextInt();
    int a[]=new int[100];
    int index=-1;
    
    for(int i=0;i<n;i++){
        a[i]=scan.nextInt();
    }
    
    int x=scan.nextInt();
    
    for(int i=0;i<n;i++){
        for(int j=0;j<n-i-1;j++){
            if(a[j]>a[j+1]){
                int temp=a[j];
                a[j]=a[j+1];
                a[j+1]=temp;
            }
        }
    }
    
    int beg,last,mid;
    beg=0;
    last=n-1;
    while(beg<=last){
        mid=(beg+last)/2;
        if(x==a[mid]){
            index=mid;
            break;
        }
        else if(x>a[mid]){
            beg=mid+1;
        }
        else{
            last=mid-1;
        }
    }


   System.out.println(index);

}

}