#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, A[100005];
  cin >> n;
  for (int i = 0; i < n; i++) cin >> A[i];
  int mx = 0;
  long long sum = 0;
  for (int i = 0; i < n; i++) {
    sum += A[i];
    if (A[i] > mx) mx = A[i];
  }
  sum -= mx;
  if (sum <= mx) {
    cout << mx - sum + 1 << endl;
  } else {
    cout << 0;
  }
  return 0;
}
