#include <bits/stdc++.h>
using namespace std;
long long a[100000], s[100000];
int main() {
  int n;
  cin >> n;
  long long sum = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    sum += a[i];
  }
  for (int i = 0; i < n; i++) {
    s[i] = sum - a[i];
  }
  long long ans = 20000000000;
  for (int i = 0; i < n; i++) {
    if (a[i] - s[i] < 0) continue;
    ans = min(ans, a[i] - s[i] + 1);
  }
  cout << ans;
}
