# Strange Currency System

Time Limit : 8 sec, Memory Limit : 131072 KB

# Problem I: 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 di erent 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\$ 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\$.

## Input

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.

## Output

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.

```4
1 2 4 8
```

```16
```

```5
1 1 3 11 2
```

## Output #2

```8
```

Source: ACM-ICPC Japan Alumni Group Winter Camp , Day 3, Tokyo, Japan, 2009-02-23
http://acm-icpc.aitea.net/