David loves playing League of Legends™. In the game League of Legends™, you must obtain a number by adding up the previous two numbers in the series. This series is called the League of Legends™ Series. The series begins with ~A~ and ~B~. To help David win, tell him the ~N^{th}~ ~(1 \le N \le 42)~ term in the League of Legends™ Series.

Input Specification

The first line contains two integers ~A~ and ~B~ ~(1 \le A, B \le 10)~

The second line contains a single integer ~N~ which is the index (1 indexed) of the number in the sequence you must output.

Output Specification

Output a single integer that is the number located at the given index.

Sample Input

1 1
6

Sample Ouput

8