here the code import java.util.*;
class binary
{
public static void main(String args[])
{
int size,i,key,first=0,last,mid;
Scanner scan=new Scanner(System.in);
size=scan.nextInt();
int arr[]=new int[size];
if(size>=0)
{
for(i=0;i<size;i++)
{
if(arr[i]>=-1000000000&&arr[i]<=1000000000)
arr[i]=scan.nextInt();
}
key=scan.nextInt();
last=size-1;
mid=(first+last)/2;
while(first<=last)
{
if(arr[mid]<key)
{
first=mid+1;
}
else if(arr[mid]==key)
{
System.out.println(mid);
break;
}
else
{
last=mid-1;
}
mid=(first+last)/2;
}
if(first>last)
{
System.out.println(-1);
}
}
}
}