#include <bits/stdc++.h> using namespace std; int a[10010]; int n, m; int main (){ ios::sync_with_stdio(false); cin.tie(0); scanf("%d", &n); for (int i = 1; i <= n; i++){ scanf("%d", &a[i]); } scanf("%d", &m); if (m > 10000) printf("-1"); int i = 1, j = n; while (i < j){ int mid = (i + j) / 2; if (a[mid] == m){ printf("%d", mid); return 0; }else if (mid < m){ j = mid; }else{ i = mid; } } printf("-1"); return 0; }