#include <fstream>

using namespace std;
ifstream in("cautbin.in");
ofstream out("cautbin.out");
int main()
{
    int v[100000],n,st=0,dr,x,i,mij,gasiti=0;
    in>>n;
    in>>x;
    for(i=0; i<n; i++)
    {
        in>>v[i];
    }
    st=v[n];
    dr=v[n-1];
    mij=(st+dr)/2;
   while(gasiti=0&&st<=dr)
        {
          if(v[mij]==x)
          {
              gasiti=1;
          }
             else
             {
                 dr=mij-1;
             }
        }
        if(gasiti==0)
        {
            out<<-1<<endl;

        }
        else
        {
            out<<v[mij]<<endl;
        }

    return 0;
}