A sorting line holds n parcels arranged in a single row, each stamped with a non-negative integer code. A dispatch robot processes the row in repeated steps: on each step, if at least two parcels remain in the row, the robot removes the parcel currently at the front and the parcel currently at the back, writes the front parcel's code directly followed by the back parcel's code — as decimal digit strings, with no separator — to form one merged numeric code, and adds that merged code to a running total. If exactly one parcel remains with nothing left to pair it with, the robot adds that parcel's own code to the total instead, and the row is then empty. This continues, always taking whatever is currently the front and back, until the row has no parcels left. Determine the final total.

Input format

The first line contains a single integer n. The second line contains n integers, the codes of the parcels in their original left-to-right order.

Output format

A single integer: the final total after processing the entire row as described above.

Constraints

• 1 <= n <= 2*10^5
• 0 <= code_i <= 9999 for every parcel

3
15 6 3

159

4
4 4 4 4

88