#include<iostream>

#define MAX_SIZE 102

using namespace std;

template <class T>

int BinarySearch(T a[],const T&x,int n,int left,int right)

{

if(left>=right)

return -1;

else

{

if(a[(left+right)/2]==x)

return (left+right)/2;

else if(x>=(left+right)/2)

return BinarySearch(a,x,n,(left+right)/2+1,right);

else if(x<(left+right)/2)

return BinarySearch(a,x,n,left,(left+right)/2-1);

}

}

int main()

{

int a[MAX_SIZE];

int i,len,x,p;

cin>>len;

for(i=0;i<len;i++)

cin>>a[i];

cin>>x;

p=BinarySearch(a,x,len,0,len-1);

if(p==-1)

cout<<"該數不存在！"<<endl;

else

cout<<p+1<<endl;

return 0;

}