Problem:
Score : 400 points

Problem Statement

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.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

-10^9 \leq A_i \leq 10^9

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the maximum possible value of B_1 + B_2 + ... + B_N.

Sample Input 1

3
-10 5 -4

Sample Output 1

19

If we perform the operation as follows:

Choose 1 as i, which changes the sequence to 10, -5, -4.

Choose 2 as i, which changes the sequence to 10, 5, 4.

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.

Sample Input 2

5
10 -4 -8 -11 3

Sample Output 2

30

Sample Input 3

11
-1000000000 1000000000 -1000000000 1000000000 -1000000000 0 1000000000 -1000000000 1000000000 -1000000000 1000000000

Sample Output 3

10000000000

The output may not fit into a 32-bit integer type.

Solution in Python (3.4.3) (judge verdict: Wrong Answer)

"""
python3 main.py < input.txt
"""
import math
import itertools as it
import heapq
"""
A,B,T=map(int, input().split())
print(int(math.floor((T+0.5)/(A))*B))
"""
"""
N=int(input())
V=list(map(int, input().split()))
C=list(map(int, input().split()))
print(sum([V[i] - C[i] for i in range(N) if V[i] - C[i] > 0]))
"""
"""
N=int(input())
A=list(enumerate(map(int, input().split())))
l=list(A)
l.sort()

x=(-1, -1)
y=(-1, -1)

while l[0][1] != 0:
        l=list(map(lambda it: (it[0], it[1]%l[0][1]), l[1:]))
        (i, xi) = x
"""
N=int(input())
A=list(map(int, input().split()))
nNeg = len([1 for a in A if a < 0])
minAbs = min(A, key=lambda ai: abs(ai))
if nNeg%2 == 0:
        print(sum([abs(ai) for ai in A]))
else:
        print(-2*minAbs + sum([abs(ai) for ai in A]))