## IPSC 2001

## Problem R – Strange Currency

The central bank of a certain state decided to cut down use of cash and
devised a monstrous plan. They want to introduce a new set of denominations
which will not allow some prices to be paid by cash. For example, if the
new set consists of banknotes with face values 5, 7, 11, the sums
1,2,3,4,6,8,9 and 13 cannot be paid. Your task is to determine the largest
sum that cannot be paid using banknotes from the given set.
(You have an unlimited supply of banknotes of each value.)

### Input file description

The input file consists of several cases. The first line of each case
contains a positive integer **N** specifying the number of denominations
in the set. The following **N** lines contain face values of the banknotes
in the ascending order, one per line. The set never contains a banknote of
value 1.
There is an empty line after each test case.
The last case is followed by a line containing a single `0`.

### Output file description

The output file contains an answer to each case in a separate line. Output
`0` if arbitrarily large sums cannot be paid using the given set
of banknotes.

### Example

**Input:**
2
1000
2000
3
5
7
11
0

**Output:**
0
13