#include<iostream.h>
#include<fstream.h>



int a[100],v,l,h,m,n;


int binsrc(int val) {
       int l = 0;
       int h = n - 1;
       while (l <= h) {
           int m = (l + h) / 2;
           if (a[m] > val)
               h = m - 1;
           else if (a[m] < val)
               l = m + 1;
           else
               return m ;
       }
       return -1 ;
};


int main()



{




    fstream f("cautbin.in",ios::in);
    fstream g("cautbin.out",ios::out);

    f>>n;
    f>>v;
    for(int i=1;i<=n;i++)
    f>>a[i];
    g<<binsrc(v);
    f.close();
    return 0;

}