Score : 400 points
There are N integers, A1,A2,...,AN, 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≤i≤N−1. Multiply both Ai and Ai+1 by −1.
Let B1,B2,...,BN be the integer sequence after your operations.
Find the maximum possible value of B1+B2+...+BN.
Input is given from Standard Input in the following format:
N A1 A2 ... AN
Print the maximum possible value of B1+B2+...+BN.
3 -10 5 -4
19
If we perform the operation as follows:
we have B1=10,B2=5,B3=4. The sum here, B1+B2+B3=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.