/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner s=new Scanner(System.in);
		int a[]={-100,-23,-5,0,12,19,27,36,79,100,191};
		int low=0,high=a.length-1;
		int key=90,ans=-1;
		ans=binarySearch(a,low,high,key);
		System.out.println(ans);
		
	}
	public static int binarySearch(int A[],int low,int high,int key){
		
		if(low==high){
			if(A[low]==key){
				return low;
			}
			else{
				return 0;
			}
		}
		else{
			if(low>=high){
				return -1;
			}
			int mid=low+(high-low)/2;
			if(A[mid]==key){
				return mid;
			}
			if(key<A[mid]){
				return binarySearch(A,low,mid-1,key);
			}
			else{
				return binarySearch(A,mid+1,high,key);
			}
		}
		
		
	}
}