Even Sum Modulo Calculation

You are given an array of integers. Compute the sum of the array elements. If the sum is even, output the sum modulo \(10^9+7\); otherwise, output -1.

In other words, let \(S\) be the sum of the array. If \(S \bmod 2 = 0\), then print \(S \bmod (10^9+7)\); otherwise, print -1.

inputFormat

The first line contains an integer \(N\) representing the number of elements in the array. The second line contains \(N\) space-separated integers.

outputFormat

Output a single integer: the sum of the array modulo \(10^9+7\) if the sum is even, or -1 if the sum is odd.

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