#include <bits/stdc++.h>
const int N = 1e5 + 1;
int a[N], n, ans;
long long sum;
void putInp() {
  scanf("%d\n", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d ", &a[i]);
    sum += a[i];
  }
}
void solve() {
  std::sort(a, a + n);
  if (a[n - 1] >= sum - a[n - 1]) {
    ans = a[n - 1] * 2 - sum + 1;
  }
}
int main() {
  putInp();
  solve();
  printf("%d\n", ans);
  return 0;
}
