#include <bits/stdc++.h>
using namespace std;
using uint = unsigned;
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vs = vector<string>;
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  return os << '(' << p.first << ',' << p.second << ')';
}
template <typename Tuple>
void print_tuple(ostream&, const Tuple&) {}
template <typename Car, typename... Cdr, typename Tuple>
void print_tuple(ostream& os, const Tuple& t) {
  print_tuple<Cdr...>(os, t);
  os << (sizeof...(Cdr) ? "," : "") << get<sizeof...(Cdr)>(t);
}
template <typename... Args>
ostream& operator<<(ostream& os, const tuple<Args...>& t) {
  print_tuple<Args...>(os << '(', t);
  return os << ')';
}
template <typename Ch, typename Tr, typename C>
basic_ostream<Ch, Tr>& operator<<(basic_ostream<Ch, Tr>& os, const C& c) {
  os << '[';
  for (auto i = begin(c); i != end(c); ++i)
    os << (i == begin(c) ? "" : " ") << *i;
  return os << ']';
}
constexpr int INF = 1e9;
constexpr int MOD = 1e9 + 7;
constexpr double EPS = 1e-9;
int main() {
  for (int n; cin >> n && n;) {
    vi a(n);
    for (int i = int(0); i < int(n); i++) cin >> a[i];
    ll mx = *max_element(begin(a), end(a)),
       sum = accumulate(begin(a), end(a), 0ll);
    cout << max<ll>(2 * mx - sum, 0) + 1 << endl;
  }
}
