Score : 400 points
There are N integers, A_1, A_2, ..., A_N, arranged in a row in this order.
You can perform the following operation on this integer sequence any number of times:
Operation: Choose an integer i satisfying 1 \leq i \leq N-1. Multiply both A_i and A_{i+1} by -1.
Let B_1, B_2, ..., B_N be the integer sequence after your operations.
Find the maximum possible value of B_1 + B_2 + ... + B_N.
Input is given from Standard Input in the following format:
N A_1 A_2 ... A_N
Print the maximum possible value of B_1 + B_2 + ... + B_N.
3 -10 5 -4
19
If we perform the operation as follows:
we have B_1 = 10, B_2 = 5, B_3 = 4. The sum here, B_1 + B_2 + B_3 = 10 + 5 + 4 = 19, is the maximum possible result.
5 10 -4 -8 -11 3
30
11 -1000000000 1000000000 -1000000000 1000000000 -1000000000 0 1000000000 -1000000000 1000000000 -1000000000 1000000000
10000000000
The output may not fit into a 32-bit integer type.