#include<stdio.h>
int binary_search(int a[],int n,int x)
int main()
{
    int n;
    scanf("%d",&n);
    int a[n],i;
    for(i=0;1<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    int x;
    scanf("%d",&x);
    
    printf("%d",binary_search(a[],n,x);
    
}
int binary_search(int a[],int n,int x)
{
    int s=0;
    int d=n-1;
    while(s<n)
    {
        int mid=(s+d)/2;
        if(a[mid]==x)
        {
            return mid;
        }
        else if (a[mid]<x)
        {
          s=mid+1 ; 
        }
        else
        {
            e=mid-1;
        }
    }
}