#include<iostream>
#include<vector>
using namespace std;
vector<int>a;
//区间是左闭右闭
int search1(vector<int>& nums,int targer)
{
    int left = 0;
    int right = nums.size() - 1;
    while(left <= right)
    {
        int middle = left + (right - left)/2;
        if(nums[middle] < targer)
        {
            left = middle + 1;
        }
        else if(nums[middle] > targer)
        {
            right = middle - 1;
        }
        else
        {
            return middle;
        }
    }
    return -1;
}
// 区间是左闭右开
int search2(vector<int>& nums,int targer)
{
    int left = 0;
    int right = nums.size()-1;
    while(left < right)
    {
        int middle = left + (right - left)/2;
        if(nums[middle] < targer)
        {
            left = middle + 1;
        }
        else if (nums[middle] > targer)
        {
            right = middle;
        }
        else
        {
            return middle;
        }
    }
    return -1;
}
int main()
{
    int n;
    while(1)
    {
        cin >> n;
        a.push_back(n);
        if(cin.get()=='\n')
        {
            break;
        }
    }
    int tag;
    cin >> tag;
    int res; 
    // res = search1(a,tag);
    res = search2(a,tag);
    cout << res ;
    return 0;
}