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)

N=int(input())
A=[_ for _ in map(int,input().split())]
#マイナスの数を求める#
minus_count=0
for i in A:
  if i<0:
    minus_count=+1
#Aの列絶対値をつけて足す#
ans=0
flag=1
for i in A:
  ans+=abs(i)
  if i==0:
    flag=0
#マイナスの数が偶数の場合、絶対値Bを全部足す#
if minus_count %2==0 or flag==0:
  print(ans)

#マイナスの数が奇数の場合、合計値から一番小さい値を二倍して引く# 
 
else:
  for i in range(N):
    A[i]=abs(A[i])
 
  print(ans-2*min(A))