AT_abc403_a [ABC403A] Odd Position Sum

You are given a sequence of positive integers of length $ N $ : $ A=(A_1,A_2,\dots,A_N) $ . Find the sum of the odd-indexed elements of $ A $ . That is, find $ A_1 + A_3 + A_5 + \dots + A_m $ , where $ m $ is the largest odd number not exceeding $ N $ .

The input is given from Standard Input in the following format: > $ N $ $ A_1 $ $ A_2 $ $ \dots $ $ A_N $

Print the answer.

### Sample Explanation 1 The sum of the odd-indexed elements of $ A $ is $ A_1+A_3+A_5+A_7=3+4+5+2=14 $ . ### Constraints - $ 1 \le N \le 100 $ - $ 1 \le A_i \le 100 $ - All input values are integers.