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 java.io.*;
  import java.util.*;
  
  public class Main {
      static long gcd(long a, long b) {
          while (b != 0) {
              long buf = a;
              a = b;
              b = buf % b;
          }
          return a;
      }
  
      public static void main(String[] args) throws IOException {
          int t = nextInt();
          while (t-- != 0) {
              int n = nextInt();
              long[] a = new long[n];
              for (int i = 0; i < n; i++) {
                  a[i] = nextLong();
              }
              long[] ans = new long[n];
              if (n % 2 == 0) {
                  for (int i = 0; i < n; i += 2) {
                      long x = Math.abs(a[i]);
                      long y = Math.abs(a[i + 1]);
                      long lcm = x * y / gcd(x, y);
                      long d1 = lcm / x;
                      long d2 = lcm / y;
                      if ((a[i] <= 0 && a[i + 1] <= 0) || (a[i] > 0 && a[i + 1] > 0)) {
                          ans[i] = d1;
                          ans[i + 1] = -d2;
                      } else {
                          ans[i] = d1;
                          ans[i + 1] = d2;
                      }
                  }
              }
              else{
                  for (int i = 0; i < n-2; i += 2) {
                      long x = Math.abs(a[i]);
                      long y = Math.abs(a[i + 1]);
                      long lcm = x * y / gcd(x, y);
                      long d1 = lcm / x;
                      long d2 = lcm / y;
                      if ((a[i] <= 0 && a[i + 1] <= 0) || (a[i] > 0 && a[i + 1] > 0)) {
                          ans[i] = d1;
                          ans[i + 1] = -d2;
                      } else {
                          ans[i] = d1;
                          ans[i + 1] = d2;
                      }
                  }
                  long x1=Math.abs(a[n-3]);
                  long x2=Math.abs(a[n-2]);
                  long x3=Math.abs(a[n-1]);
                  long l=x1*x2/gcd(x1,x2);
                  long r=l*x3/gcd(l,x3);
                  ans[n-3]=r/x1;
                  ans[n-2]=r/x2;
                  if(a[n-3]<=0)ans[n-3]=-r/x1;
                  if(a[n-2]<=0)ans[n-2]=-r/x2;
                  long q=a[n-3]*ans[n-3]+a[n-2]*ans[n-2];
                  if(a[n-1]<=0)ans[n-1]=q/x3;
                  else ans[n-1]=-q/x3;
              }
              for (int i = 0; i < n; i++) {
                  out.print(ans[i]+" ");
              }
              out.println();
          }
          out.close();
      }
  
      static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      static PrintWriter out = new PrintWriter(System.out);
      static StringTokenizer in = new StringTokenizer("");
  
  
      public static boolean hasNext() throws IOException {
          if (in.hasMoreTokens()) return true;
          String s;
          while ((s = br.readLine()) != null) {
              in = new StringTokenizer(s);
              if (in.hasMoreTokens()) return true;
          }
          return false;
      }
  
      public static String nextToken() throws IOException {
          while (!in.hasMoreTokens()) {
              in = new StringTokenizer(br.readLine());
          }
          return in.nextToken();
      }
  
      public static int nextInt() throws IOException {
          return Integer.parseInt(nextToken());
      }
  
      public static long nextLong() throws IOException {
          return Long.parseLong(nextToken());
      }
  
      public static double nextDouble() throws IOException {
          return Double.parseDouble(nextToken());
      }
  }
  
  class Ayo {
      int v;
      long w;
  
      public Ayo(int v, long w) {
          this.v = v;
          this.w = w;
      }
  }
  
  class Ayo1 implements Comparable<Ayo1> {
      long w;
      int v;
  
      public Ayo1(long w, int v) {
          this.w = w;
          this.v = v;
      }
  
      @Override
      public int compareTo(Ayo1 o) {
          if (o.v == v && o.w == w) return 0;
          else {
              if (w < o.w) return -1;
              else if (w > o.w) return 1;
              else {
                  return Integer.compare(v, o.v);
              }
          }
      }
  }