Maximum Alternating Subsequence Sum

Given an integer array nums of length n, you may choose a subsequence (not necessarily contiguous, but order preserved). Define the subsequence's alternating sum as: x0 - x1 + x2 - x3 + ... (0-indexed: add even positions, subtract odd positions). Return the maximum alternating sum you can obtain. Input (stdin) Line 1: integer n. Line 2: n integers representing nums. Output (stdout) Print one integer: the maximum alternating sum. Constraints 1 <= n <= 2*10^5 1 <= nums[i] <= 1e9 Example Input 4 4 2 5 3 Output 7