description: Vupsen and Pupsen were gifted an integer array. Since Vupsen doesn't like the number 0, he threw away all numbers equal to 0 from the array. As a result, he got an array a of length n.
  
  Pupsen, on the contrary, likes the number 0 and he got upset when he saw the array without zeroes. To cheer Pupsen up, Vupsen decided to come up with another array b of length n such that ∑_{i=1}^{n}a_i ⋅ b_i=0. Since Vupsen doesn't like number 0, the array b must not contain numbers equal to 0. Also, the numbers in that array must not be huge, so the sum of their absolute values cannot exceed 10^9. Please help Vupsen to find any such array b!
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 100) — the number of test cases. The next 2 ⋅ t lines contain the description of test cases. The description of each test case consists of two lines.
  
  The first line of each test case contains a single integer n (2 ≤ n ≤ 10^5) — the length of the array.
  
  The second line contains n integers a_1, a_2, …, a_n (-10^4 ≤ a_i ≤ 10^4, a_i ≠ 0) — the elements of the array a.
  
  It is guaranteed that the sum of n over all test cases does not exceed 2 ⋅ 10^5.
  
  Output
  
  For each test case print n integers b_1, b_2, …, b_n — elements of the array b (|b_1|+|b_2|+… +|b_n| ≤ 10^9, b_i ≠ 0, ∑_{i=1}^{n}a_i ⋅ b_i=0).
  
  It can be shown that the answer always exists.
  
  Example
  
  Input
  
  
  3
  2
  5 5
  5
  5 -2 10 -9 4
  7
  1 2 3 4 5 6 7
  
  
  Output
  
  
  1 -1
  -1 5 1 -1 -1
  -10 2 2 -3 5 -1 -1
  
  Note
  
  In the first test case, 5 ⋅ 1 + 5 ⋅ (-1)=5-5=0. You could also print 3 -3, for example, since 5 ⋅ 3 + 5 ⋅ (-3)=15-15=0
  
  In the second test case, 5 ⋅ (-1) + (-2) ⋅ 5 + 10 ⋅ 1 + (-9) ⋅ (-1) + 4 ⋅ (-1)=-5-10+10+9-4=0.
solution: import math
  
  
  def GCD(a, b, c):
      if a< 0:
          a = -a
      if b<0:
          b=-b
      if c<0:
          c= -c
      d = math.gcd(a, b)
      d = math.gcd(d,c)
      return d
  
  
  def GCDT(a, b):
      if a< 0:
          a = -a
      if b<0:
          b=-b
      d = math.gcd(a, b)
      return d
  
  
  
  
  n = int(input())
  for i in range(n):
      len = int(input())
      lineX = input().split()
      line = []
      for s in lineX:
          line.append(int(s))
      i = 0
      if len % 2 == 1:
          a = line[1]+line[2]
          b = -line[0]
          c = -line[0]
          if a == 0:
              a = line[1] - line[2]
              c = -c
          d = GCD(a, b, c)
          print(str(int(a/d)), str(int(b/d)), str(int(c/d)), end='')
          i = 3
      while i<len:
          if i!=0:
              print(' ', end='')
          a = line[i]
          b = line[i+1]
          d = GCDT(a, b)
          a = int(a/d)
          b = int(b/d)
          print(str(b), str(-a), end='')
          i += 2
      print()
  