#include <bits/stdc++.h>
using namespace std;
int N, n, maxl = 0, cnt = 0;
int main() {
  scanf("%d", &N);
  for (int i = 0; i < N; i++) {
    scanf("%d", &n);
    if (n > maxl) {
      cnt += maxl;
      maxl = n;
    } else {
      cnt += n;
    }
  }
  printf("%d\n", maxl - cnt + 1);
}
