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 {
  
  
      public static void main(String[] args) throws IOException {
          StdIn scn = new StdIn();
          int t = scn.nextInt();
          while (t-- > 0) {
              int n = scn.nextInt();
              int[] arr = scn.readIntArray(n);
              int[] ans = new int[n];
              if (n % 2 == 0) {
                  for (int i = 0; i < n; i = i + 2) {
                      ans[i] = -arr[i + 1];
                      ans[i + 1] = arr[i];
                  }
                  scn.printIntArray(ans);
              } else {
                  for (int i = 0; i < n - 3; i = i + 2) {
                      ans[i] = -arr[i + 1];
                      ans[i + 1] = arr[i];
                  }
                  if (arr[n - 1] + arr[n - 2] != 0) {
                      ans[n - 1] = -arr[n - 3];
                      ans[n - 2] = -arr[n - 3];
                      ans[n - 3] = arr[n - 1] + arr[n - 2];
                  }else if (arr[n - 2] + arr[n - 3] != 0){
                      ans[n - 2] = -arr[n - 1];
                      ans[n - 3] = -arr[n - 1];
                      ans[n - 1] = arr[n - 2] + arr[n - 3];
                  }else{
                      ans[n - 1] = -arr[n - 2];
                      ans[n - 3] = -arr[n - 2];
                      ans[n - 2] = arr[n - 1] + arr[n - 3];
                  }
                  scn.printIntArray(ans);
              }
          }
      }
  
      interface Input {
  
          public String next();
  
          public String nextLine();
  
          public int nextInt();
  
          public long nextLong();
  
          public double nextDouble();
      }
  
      static class StdIn implements Input {
          final private int BUFFER_SIZE = 1 << 16;
          private DataInputStream din;
          private byte[] buffer;
          private int bufferPointer, bytesRead;
  
          public StdIn() {
              din = new DataInputStream(System.in);
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          public StdIn(String filename) {
              try {
                  din = new DataInputStream(new FileInputStream(filename));
              } catch (Exception e) {
                  throw new RuntimeException();
              }
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          public String next() {
              int c;
              while ((c = read()) != -1 && (c == ' ' || c == ' ' || c == ' ')) ;
              StringBuilder s = new StringBuilder();
              while (c != -1) {
                  if (c == ' ' || c == ' ' || c == ' ')
                      break;
                  s.append((char) c);
                  c = read();
              }
              return s.toString();
          }
  
          public String nextLine() {
              int c;
              while ((c = read()) != -1 && (c == ' ' || c == ' ' || c == ' ')) ;
              StringBuilder s = new StringBuilder();
              while (c != -1) {
                  if (c == ' ' || c == ' ')
                      break;
                  s.append((char) c);
                  c = read();
              }
              return s.toString();
          }
  
          public int nextInt() {
              int ret = 0;
              byte c = read();
              while (c <= ' ')
                  c = read();
              boolean neg = (c == '-');
              if (neg)
                  c = read();
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
  
              if (neg)
                  return -ret;
              return ret;
          }
  
          public long me(long x, long y, long p) {
              long res = 1;
              x = x % p;
              if (x == 0) {
                  return 0;
              }
              while (y > 0) {
                  if ((y & 1) != 0) {
                      res = (res * x) % p;
                  }
                  y = y >> 1;
                  x = (x * x) % p;
              }
              return res;
          }
  
          public int[] readIntArray(int n) {
              int[] ar = new int[n];
              for (int i = 0; i < n; ++i)
                  ar[i] = nextInt();
              return ar;
          }
  
          public long nextLong() {
              long ret = 0;
              byte c = read();
              while (c <= ' ')
                  c = read();
              boolean neg = (c == '-');
              if (neg)
                  c = read();
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
              if (neg)
                  return -ret;
              return ret;
          }
  
          public long[] readLongArray(int n) {
              long[] ar = new long[n];
              for (int i = 0; i < n; ++i)
                  ar[i] = nextLong();
              return ar;
          }
  
          public long gcd(long a, long b) {
              if (b == 0) {
                  return a;
              }
              return gcd(b, a % b);
          }
  
          public int ncr(int N, int r) {
              double ans = 1;
              for (int i = 1; i <= r; i++) {
                  ans = ans * (N - r + i) / i;
              }
              return (int) ans;
          }
  
          public void printLongArray(long[] a) {
              for (int i = 0; i < a.length; i++) {
                  System.out.print(a[i] + " ");
              }
              System.out.println();
          }
  
          public void printIntArray(int[] a) {
              for (int i = 0; i < a.length; i++) {
                  System.out.print(a[i] + " ");
              }
              System.out.println();
          }
  
          public double nextDouble() {
              double ret = 0, div = 1;
              byte c = read();
              while (c <= ' ')
                  c = read();
              boolean neg = (c == '-');
              if (neg)
                  c = read();
  
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
  
              if (c == '.') {
                  while ((c = read()) >= '0' && c <= '9') {
                      ret += (c - '0') / (div *= 10);
                  }
              }
  
              if (neg)
                  return -ret;
              return ret;
          }
  
          private void fillBuffer() throws IOException {
              bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
              if (bytesRead == -1)
                  buffer[0] = -1;
          }
  
          private byte read() {
              try {
                  if (bufferPointer == bytesRead)
                      fillBuffer();
                  return buffer[bufferPointer++];
              } catch (IOException e) {
                  throw new RuntimeException();
              }
          }
  
          public void close() throws IOException {
              if (din == null)
                  return;
              din.close();
          }
      }
  }