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 sys
  input = sys.stdin.buffer.readline
  
  
  def check(a, b):
      res = 0
      for i in range(n):
          res += a[i] * b[i]
      return res
  
  
  def gcd(a, b):
      while b:
          a, b = b, a % b
      return a
  
  
  t = int(input())
  for _ in range(t):
      n = int(input())
      a = list(map(int, input().split()))
  
      b = [0] * n
      if n % 2 == 0:
          for i in range(n // 2):
              l, r = i * 2, i * 2 + 1
              b[l] = a[r]
              b[r] = -a[l]
  
      else:
          array = sorted([(abs(val), val, i) for i, val in enumerate(a)], reverse=True)
          stack = []
          
          for _, val, i in array[:-2]:
              if not stack:
                  stack.append((val, i))
                  continue
              v, j = stack[-1]
              if abs(val) == abs(v):
                  if val == v:
                      b[i] = -1
                      b[j] = 1
                  else:
                      b[i] = 1
                      b[j] = 1
                  stack.pop()
              else:
                  stack.append((val, i))
  
          for _, val, i in array[-2:]:
              stack.append((val, i))
  
          vi, i = stack.pop()
          vj, j = stack.pop()
          vk, k = stack.pop()
          b[i] = vj + vk
          b[j] = -vi + vk
          b[k] = -vi - vj
  
          while stack:
              vl, l = stack.pop()
              vr, r = stack.pop()
              b[l] = vr
              b[r] = -vl
  
      idx = -1
      for i in range(n):
          if b[i] == 0:
              idx = i
      if idx == -1:
          print(*b)
          continue
  
      nxt_idx = (idx + 1) % n
      val1 = a[nxt_idx] // gcd(a[idx], a[nxt_idx])
      val2 = -a[idx] // gcd(a[idx], a[nxt_idx])
      if b[nxt_idx] + val2 != 0:
          b[idx] += val1
          b[nxt_idx] += val2
      else:
          b[idx] -= val1
          b[nxt_idx] -= val2 
      
      print(*b)
      # print(check(a, b))