#include <bits/stdc++.h> using namespace std; int a[11000]; int main(){ int n, m; cin >> n; for(int i = 1; i <= n; i++){ cin >> a[i]; } cin >> m; int l = 1; r = n; while(l <= r){ int mid = (l + r) / 2; if(a[mid] == m){ cout << mid; return 0; } else if(a[mid] < m){ l = mid + 1; } else { r = mid - 1; } } cout << -1; return 0; }