Official algorithmic problem description and constraints.
You have an array π of π integers.
You perform exactly π operations on it. In one operation, you select any contiguous subarray of the array π (possibly empty) and insert the sum of this subarray anywhere in the array.
Your task is to find the maximum possible sum of the array after πsuch operations.
As this number can be very large, output the answer modulo 10^9+7.
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