Buggy python submission (verdict: Runtime Error):
-*- using:utf-8 -*-

def count_negative(n,a):
    count = 0
    for i in range(n):
        if a[i] == 0:
            return 0
        elif a[i] < 0:
            count += 1
    return count

def num_of_min(n,a):
    minimum = max(a)
    count = 0
    tmp = 0
    for i in range(n):
        tmp = abs(a[i])
        if tmp < minimum:
            minimum = tmp
            count = i
        else:
            pass
    return count

def flipping(n,a):
    nc = count_negative(n,a)
    total = 0
    count = 0
    if nc % 2 == 0:
        for i in range(n):
            total += abs(a[i])
    else:
        count = num_of_min(n,a)
        target = a.pop(count)

        k = n - 1
        for i in range(k):
            total += abs(a[i])
        else:
            total += target*(-1)

    return total

if __name__ == '__main__':
    n = int(raw_input())
    a = map(int,raw_input().split())
    gt = flipping(n,a)
    print("%d" %gt)

Fixed submission:
#-*- using:utf-8 -*-

def count_negative(n,a):
    count = 0
    for i in range(n):
        if a[i] == 0:
            return 0
        elif a[i] < 0:
            count += 1
    return count

def num_of_min(n,a):
    minimum = sum(map(abs,a))
    
    count = 0    
    tmp = 0
    for i in range(n):
        tmp = abs(a[i])
        if tmp < minimum:
            minimum = tmp
            count = i
        else:
            pass
    return count

def flipping(n,a):
    nc = count_negative(n,a)
    total = 0
    count = 0
    if nc % 2 == 0:
        total = sum(map(abs,a))
    else:
        count = num_of_min(n,a)
        target = a.pop(count)
        
        total = sum(map(abs,a))
        if target > 0:
            total += target*(-1)
        else:
            total += target

    return total

if __name__ == '__main__':
    n = int(raw_input())
    a = map(int,raw_input().split())
    gt = flipping(n,a)
    print("%d" %gt)

Buggy python submission (verdict: Runtime Error):
-*- using:utf-8 -*-

def count_negative(n,a):
    count = 0
    for i in range(n):
        if a[i] == 0:
            return 0
        elif a[i] < 0:
            count += 1
    return count

def num_of_min(n,a):
    minimum = max(a)
    count = 0
    tmp = 0
    for i in range(n):
        tmp = abs(a[i])
        if tmp < minimum:
            minimum = tmp
            count = i
        else:
            pass
    return count

def flipping(n,a):
    nc = count_negative(n,a)
    total = 0
    count = 0
    if nc % 2 == 0:
        for i in range(n):
            total += abs(a[i])
    else:
        count = num_of_min(n,a)
#            print("i %d, a[i] %d, count %d" %(i,a[i],count))
        target = a.pop(count)

        k = n - 1
        for i in range(k):
            total += abs(a[i])
#            print("i %d, tmp total %d" %(i,total))
        else:
            total += target*(-1)

    return total

if __name__ == '__main__':
    n = int(raw_input())
    a = map(int,raw_input().split())
    gt = flipping(n,a)
    print("%d" %gt)

Fixed submission:
#-*- using:utf-8 -*-

def count_negative(n,a):
    count = 0
    for i in range(n):
        if a[i] == 0:
            return 0
        elif a[i] < 0:
            count += 1
    return count

def num_of_min(n,a):
    minimum = sum(map(abs,a))
    
    count = 0    
    tmp = 0
    for i in range(n):
        tmp = abs(a[i])
        if tmp < minimum:
            minimum = tmp
            count = i
        else:
            pass
    return count

def flipping(n,a):
    nc = count_negative(n,a)
    total = 0
    count = 0
    if nc % 2 == 0:
        total = sum(map(abs,a))
    else:
        count = num_of_min(n,a)
        target = a.pop(count)
        
        total = sum(map(abs,a))
        if target > 0:
            total += target*(-1)
        else:
            total += target

    return total

if __name__ == '__main__':
    n = int(raw_input())
    a = map(int,raw_input().split())
    gt = flipping(n,a)
    print("%d" %gt)