#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
const int INF = 1e9;
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using vc = vector<char>;
using vii = vector<vi>;
using vll = vector<vl>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vpii = vector<pii>;
using vpll = vector<pll>;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  vl v(n);
  ll sum = 0;
  for (int i = (0); i < (n); i++) {
    cin >> v[i];
    sum += v[i];
  }
  ll m = *max_element(v.begin(), v.end());
  sum -= m;
  if (sum > m)
    cout << "0\n";
  else
    cout << m - sum + 1 << endl;
  return 0;
}
