#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, a, b, c;
  int v[100000];
  do {
    cin >> n;
  } while (3 > n || n > 100000);
  for (i = 0; i < n; i++) {
    do {
      cin >> v[i];
    } while (v[i] < 1 || v[i] > 1000000000);
  }
  a = v[0];
  for (i = 0; i < n - 1; i++) {
    if (v[i + 1] > a) {
      a = v[i + 1];
    }
  }
  b = 0;
  for (i = 0; i < n; i++) {
    b = b + v[i];
  }
  b = b - a;
  if ((a - b) < 0) {
    c = b - a + 1;
  } else {
    c = a - b + 1;
  }
  cout << c;
  return 0;
}
