# Problem: Travelling Salesperson

Want to try solving this problem? You can submit your code online if you log in or register.

## Travelling Salesperson

**Input File:** `salesin.txt`
**Output File:** `salesout.txt`
**Time Limit:** 1 second

Even in uncertain economic times, no home can be without electrical
appliances. Realising that there is still a sales opportunity, you
have recently taken up a part-time job selling electrical appliances
the old fashioned way--travelling door to door. However, your hometown of Perth
is full of electrical salespeople who have cornered the market, and
so you must travel across Australia to find customers.

You will start in your hometown, Perth, drive across Australia to
Sydney, and then back again to Perth. There are three routes between
Perth and Sydney. In your market research, you have counted the
number of customers living along each route. You wish to plan your
trip to Sydney and back so that you visit the greatest number of customers possible. You
must take a different route on the return journey, otherwise you
would simply end up visiting the same satisfied customers twice.

Your task is to write a program which, given the number of customers
along each of the three routes between Perth and Sydney, determines
the greatest number of customers you can visit by travelling from
Perth to Sydney and back.

### Input

The input file will consist of three lines, each containing a single
integer (whole number), representing the number of customers on the
northern, central and southern routes respectively. Each route will
contain between 0 and 1000000 customers, inclusive.

### Output

The output file should consist of a single integer: the greatest number of
customers you can visit by driving from Perth to Sydney and back
again.

### Sample Input

500
300
700

### Sample Output

1200

### Explanation

The sample input is demonstrated in the diagram below.

To ensure you visit the greatest number of customers in this case,
you should travel the southern route to visit 700
customers on the way to Sydney, then return via the northern route to
visit 500 customers on the way back for a total of 1200 customers.
Alternately, you could take the northern route first, and return via
the southern route, however the maximum number of customers you can
visit is 1200.

### Scoring

The score for each input scenario will be 100% if the correct answer is written to the output file, and 0% otherwise.