#include <bits/stdc++.h>

using namespace std;

int Sort(int *ar, int s)
{
    int i, j;

    for( i =0; i<s-1; i++)
        for(j =i+1; j<s; j++)
        {
            if(ar[i]>ar[j])
            {
                int temp = ar[i];
                ar[i] = ar[j];
                ar[j] = temp;
            }
        }
}

 int binarysearch(int *ar,int s,int key)
 {
    int st =0, e = s,mid;
    while(st<=e)
    {
       mid = (st+e)/2;
       if(ar[mid]<key)
       {
           st = mid+1;
       }
       else if(ar[mid]>key)
       {
           e = mid-1;
       }
       else if (st>e)
       {
          // cout<<st<<" "<<e<<endl;
           return -1;
       }
       else if (ar[mid] == key)
       {
           //cout<<"mid in equal = "<<mid<<endl;
           return mid;
       }
    }
}


int main(){

  int ar[100],s,key, f;
  cout<<"give size of array\n";
  cin>>s;

  for(int i =0; i<s; i++)
  {
      cin>>ar[i];
  }

  Sort(ar,s);

  for(int i =0; i<s; i++)
  {
      cout<<ar[i]<<" ";
  }

  cout<<"enter key\n";


      cin>>key;


   // int st =0, e = s,mid, f = 0;
  /*  while(st <= e)
    {
       mid = (st+e)/2;
       if(ar[mid]<key)
          st = mid+1;

       else if(ar[mid]>key)
           e = mid-1;

       else if (st>e)
           break;

       else if (ar[mid] == key)
       {
           cout<<"mid in equal = "<<mid<<endl;
           f = 1;
           break;
       }
    }
    */
    f = binarysearch(ar,s,key);

    cout<<f<<endl;

}