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.util.Scanner;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.LinkedList;
  
  import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.io.BufferedWriter;
  import java.io.OutputStreamWriter;
  
  public class D {
  	public static void main(String[] args) {
  		try {
  			BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
  			BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
  
  			int t = Integer.parseInt(reader.readLine());
  			for (; t > 0; t--) {
  				int n = Integer.parseInt(reader.readLine());
  				int[] a = new int[n];
  				Integer[] c = new Integer[n];
  				int[] b = new int[n];
  
  				HashMap<Integer, LinkedList<Integer>> pos = new HashMap<>();
  
  				String[] line = reader.readLine().split(" ");
  
  				for (int i = 0; i < n; i++) {
  					a[i] = Integer.parseInt(line[i]);
  					c[i] = Integer.valueOf(a[i]);
  
  					LinkedList<Integer> adjs = pos.getOrDefault(a[i], new LinkedList<>());
  					adjs.add(i);
  					pos.put(a[i], adjs);
  				}
  
  				Arrays.sort(c, (x, y) -> Math.abs(x) - Math.abs(y));
  
  				int lim = n;
  				if (n % 2 == 1)
  					lim -= 3;
  
  				for (int i = 0; i+1 < lim; i+=2) {
  					Integer l = c[i]; Integer r = c[i+1];
  
  					LinkedList<Integer> lAdjs = pos.get(l);
  					LinkedList<Integer> rAdjs = pos.get(r);
  
  					Integer lPos = lAdjs.get(0);
  					lAdjs.remove(0);
  
  					Integer rPos = rAdjs.get(0);
  					rAdjs.remove(0);
  
  					int g = Math.abs(gcd(r, l));
  					b[lPos] = -r/g; b[rPos] = l/g;
  				}
  
  				int[] lp = new int[3];
  				int lPos = 0;
  
  				for (int i = 0; i < n; i++)
  					if (b[i] == 0)
  						lp[lPos++] = i;
  
  				if (n % 2 == 1) {
  					b[lp[0]] = a[lp[0]] * a[lp[2]];
  					b[lp[1]] = a[lp[1]] * a[lp[2]];
  
  					b[lp[2]] = -(a[lp[0]]*a[lp[0]] + a[lp[1]]*a[lp[1]]);
  					int g = gcd(gcd(Math.abs(b[lp[0]]), Math.abs(b[lp[1]])), Math.abs(b[lp[2]]));
   
  					for (int i = 0; i < 3; i++)
  						b[lp[i]] /= g;
  				}
  
  
  				for (int i = 0; i < n; i++) {
  					String s = String.valueOf(b[i]);
  					writer.write(s, 0, s.length());
  					writer.write(' ');
  				}
  
  				writer.flush();
  			}
  
  			writer.close();
  			reader.close();
  		} catch (Exception e) {
  			e.printStackTrace();
  		}
  	}
  
  	private static int gcd(int a, int b) {
  		if (b == 0)	return a;
  		return gcd(b, a%b);
  	}
  
  	private static void fill(int[] a, int[] b, int lim) {
  		for (int i = 0; i < lim; i+=2) {
  			int l = a[i]; int r = a[i+1];
  			b[i] = -r; b[i+1] = l;
  
  			int g = gcd(Math.abs(b[i]), Math.abs(b[i+1]));
  			b[i] /= g; b[i+1] /= g;
  		}
  	}
  }