AT_abc479_a [ABC479A] Odd Index Sum

You are given an integer sequence of length $ N $ : $ A=(A_1,A_2,\dots,A_N) $ . Find the sum of the odd-indexed terms of $ A $ . More formally, find the sum of $ A_i $ over all odd $ i $ satisfying $ 1 \le i \le N $ .

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

Output the answer.

### Sample Explanation 1 In this input, $ A=(3,1,4,1,5) $ , and the terms to be summed are $ A_1,A_3,A_5 $ . Output their sum, that is, $ 3+4+5=12 $ . ### Sample Explanation 2 In this input, $ A=(2,7,1,8,2,8) $ , and the terms to be summed are $ A_1,A_3,A_5 $ . Output their sum, that is, $ 2+1+2=5 $ . ### Constraints - All input values are integers. - $ 1 \le N \le 100 $ - $ 1 \le A_i \le 100 $