Strange Currency System

The currency system in the Kingdom of Yoax-Musty is strange and fairly inefficient. Like other countries, the kingdom has its own currencty unit denoted by K \$(kingdom dollar). However, the Ministry of Finance issues bills for every value between 1 K \\$ and (231 - 1) K \$ worth.

On the other hand, this system often enables people to make many different values just with a small number of bills. For example, if you have four bills of 1 K \$, 2 K \\$, 4 K \$, and 8 K \\$ worth respectively, you can make any values from 1 K #36; to 15 K \$.

In this problem, you are requested to write a program that finds the minimum value that cannot be made with a given set (multiset in a mathematical sense) of bills. For the case with the four bills (1 K \$, 2 K \\$, 4 K \$, and 8 K \\$), since you can make any values up to 15 K \$, your program should report 16 K$.

The input consists of two lines. The first line contains an integer N (1 ≤ N ≤ 10000), the number of bills. The second line contains N integers, each of which represents the value of a bill in K \$. There may be multiple bills of the same value.

Print the minimum value unable to be made on a line. The value should be given in K \$ and without any currency sign or name.