#include <bits/stdc++.h> using namespace std;

const int maxn = 1e6 + 100; int a[maxn];

int main() { int n; cin >> n; for (int i = 1; i <= n; i++) { cin >> a[i]; } int x, s = -1; cin >> x; for (int i = 1; i <= n; i++) { int l = 1, r = n; while (l <= r) { int mid = (l + r) / 2; if (a[mid] == x) { s = mid; break; } else if (a[mid] > x) { r = mid - 1; } else { l = mid + 1; } } } cout << s; return 0; }