#include <iostream>
#include <fstream>
using namespace std;

bool binker(int n,int temp, int ker, int t[1000])
{
    if(ker<t[0] || ker>t[n-1]){
        return 0;
    }
    else if(n==1 && t[0]==ker){
        return 1;
    }
    else if (temp==0) {
        return 0;
    }
     else if (t[n-temp-1] == ker || t[n-temp]==ker) {
        return 1;
    }
    else if (t[n-temp] > ker) {
          n=n-temp;
          temp=temp/2+1;
          return binker(n, temp, ker, t);
    }
    else  if(t[n-temp] < ker){
         temp=temp/2;
         return binker(n, temp, ker, t);
    }
}

int main()
{
    int n,temp,ker, t[1000];
    ifstream f("cautbin.in");
    ofstream g("cautbin.out");
    f >> n;
    temp=n/2;
    for (int i = 0; i < n; i++) {
        f >> t[i];
    }
    f >> ker;
    g << binker(n, temp, ker, t);
    return 0;
}