#include <iostream>
using namespace std;
int x;
int caut (int v[], int s, int d)
{

    if(s>d)
        return -1;
    else
        {
            int m = (s+d)/2;
            if (x==v[m])
               	return m;
            if (x<v[m])
                caut(v,s,m-1);
            else
                caut(v,m+1,d);
	}
}
int main (){
	x = 11;
	int v[10] = {5,7,9,11,12,16,19,21,23,24};
	cout << caut(v,0,9);
}