#include <bits/stdc++.h>
using namespace std;
unsigned long long min(unsigned long long x, unsigned long long y) {
  if (x < y) return x;
  return y;
}
unsigned long long max(unsigned long long x, unsigned long long y) {
  if (x < y) return y;
  return x;
}
long long min(long long x, long long y) {
  if (x < y) return x;
  return y;
}
long long max(long long x, long long y) {
  if (x < y) return y;
  return x;
}
double min(double x, double y) {
  if (x < y) return x;
  return y;
}
double max(double x, double y) {
  if (x < y) return y;
  return x;
}
unsigned long long gcd(unsigned long long x, unsigned long long y) {
  if (!x) return y;
  if (!y) return x;
  if (x > y) swap(x, y);
  return gcd(x, y % x);
}
unsigned long long inv(unsigned long long a, unsigned long long c) {
  if (a == 1) {
    return 1;
  }
  return ((c - (c / a)) * inv(c % a, c)) % c;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, m, x;
  cin >> n;
  m = (n + 1) / 2;
  long long a[m], sum = 0;
  for (int i = 0; i < m; ++i) {
    cin >> a[i];
    sum += a[i];
  }
  cin >> x;
  if (sum + (n - m) * x > 0) {
    cout << n << "\n";
    return 0;
  }
  m = n - m;
  long long p[m];
  p[0] = x - a[0];
  for (int i = 1; i < m; ++i) {
    p[i] = p[i - 1] + x - a[i];
  }
  for (int i = 1; i < m; ++i) {
    p[i] = min(p[i - 1], p[i]);
  }
  for (int i = 0; i < m; ++i) {
    if (sum + (m - 1 - i) * x + min(0, p[i]) > 0) {
      cout << (n - 1 - i) << "\n";
      return 0;
    }
  }
  cout << "-1\n";
  return 0;
}
