#include <bits/stdc++.h>
long long sum, mx, x;
void t_main() {
  int n;
  scanf("%d", &n);
  while (n--) {
    scanf("%I64d", &x);
    sum += x;
    if (mx < x) mx = x;
  }
  sum -= mx;
  x = mx - sum + 1;
  if (x < 1) x = 1;
  printf("%I64d\n", x);
}
void run() {
  int t = 1;
  while (t--) t_main();
}
int main() {
  run();
  return 0;
}
