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.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  public class Main1582D {
      public static void main(String[] args) {
          final FastScanner in = new FastScanner(System.in);
          final PrintWriter out = new PrintWriter(System.out);
          int t = in.nextInt();
          for (int i = 0; i < t; i++) {
              int n = in.nextInt();
              int[] a = new int[n];
              for (int j = 0; j < n; j++) {
                  a[j] = in.nextInt();
              }
              int[] b = solution(a, n);
              for (int j = 0; j < n; j++) {
                  out.print(b[j]);
                  out.print(" ");
              }
              out.println();
          }
  
          out.flush();
          out.close();
          in.close();
      }
  
      private static int[] solution(int[] a, int n) {
          int[] b = new int[n];
          int start = 0;
  
          if (n % 2 == 1) {
              if (a[0] + a[1] != 0) {
                  b[0] = -a[2];
                  b[1] = -a[2];
                  b[2] = a[0] + a[1];
              } else if (a[0] + a[2] != 0) {
                  b[0] = -a[1];
                  b[1] = a[0] + a[2];
                  b[2] = -a[1];
              } else {
                  b[0] = a[1] + a[2];
                  b[1] = -a[0];
                  b[2] = -a[0];
              }
              start = 3;
          } else {
              b[0] = -a[1];
              b[1] = a[0];
              int gcd = gcd(b[0], b[1]);
              b[0] /= gcd;
              b[1] /= gcd;
              start = 2;
          }
          for (int i = start; i < n; i += 2) {
              b[i] = -a[i + 1];
              b[i + 1] = a[i];
          }
          return b;
      }
  
      private static int gcd(int a, int b) {
          if (b == 0) return a;
          return gcd(b, a % b);
      }
  
      private static class FastScanner {
          BufferedReader br;
          StringTokenizer st;
  
          FastScanner(InputStream stream) {
              try {
                  br = new BufferedReader(new InputStreamReader(stream));
              } catch (Exception e) {
                  e.printStackTrace();
              }
          }
  
          String next() {
              while (st == null || !st.hasMoreTokens()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          double nextDouble() {
              return Double.parseDouble(next());
          }
  
          int[] readIntArr(int n) {
              int[] result = new int[n];
              for (int i = 0; i < n; i++) {
                  result[i] = Integer.parseInt(next());
              }
              return result;
          }
  
          long[] readLongArr(int n) {
              long[] result = new long[n];
              for (int i = 0; i < n; i++) {
                  result[i] = Long.parseLong(next());
              }
              return result;
          }
  
  
          void close() {
              try {
                  br.close();
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
      }
  }
  