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

int main() {
    int n, x;
    
    while (cin >> n) { // 注意 while 处理多个 case
      //  cout << a + b << endl;
      vector<int> q;
      for (int i = 0; i < n; i++) 
      {
         cin >> x;
         q.push_back(x);   //形成数组
      }
      cin >> x;
      for (int i = 0; i < n; i++) 
      {
       if (q[i] == x) 
       {
        cout << i << endl;  //搜索数组
        break;
       }
       if (i == n - 1 && q[i] != x) 
       {
       cout << -1 << endl;  //搜索失败
       }
      }

    }
}
// 64 位输出请用 printf("%lld")