description: You are given n integers a_1, a_2, …, a_n. Find the maximum value of max(a_l, a_{l + 1}, …, a_r) ⋅ min(a_l, a_{l + 1}, …, a_r) over all pairs (l, r) of integers for which 1 ≤ l < r ≤ n.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10 000) — the number of test cases.
  
  The first line of each test case contains a single integer n (2 ≤ n ≤ 10^5).
  
  The second line of each test case contains n integers a_1, a_2, …, a_n (1 ≤ a_i ≤ 10^6).
  
  It is guaranteed that the sum of n over all test cases doesn't exceed 3 ⋅ 10^5.
  
  Output
  
  For each test case, print a single integer — the maximum possible value of the product from the statement.
  
  Example
  
  Input
  
  
  4
  3
  2 4 3
  4
  3 2 3 1
  2
  69 69
  6
  719313 273225 402638 473783 804745 323328
  
  
  Output
  
  
  12
  6
  4761
  381274500335
  
  Note
  
  Let f(l, r) = max(a_l, a_{l + 1}, …, a_r) ⋅ min(a_l, a_{l + 1}, …, a_r).
  
  In the first test case, 
  
    * f(1, 2) = max(a_1, a_2) ⋅ min(a_1, a_2) = max(2, 4) ⋅ min(2, 4) = 4 ⋅ 2 = 8. 
    * f(1, 3) = max(a_1, a_2, a_3) ⋅ min(a_1, a_2, a_3) = max(2, 4, 3) ⋅ min(2, 4, 3) = 4 ⋅ 2 = 8. 
    * f(2, 3) = max(a_2, a_3) ⋅ min(a_2, a_3) = max(4, 3) ⋅ min(4, 3) = 4 ⋅ 3 = 12. 
  
  
  
  So the maximum is f(2, 3) = 12.
  
  In the second test case, the maximum is f(1, 2) = f(1, 3) = f(2, 3) = 6.
solution: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.StringTokenizer;
  
  public class A implements Runnable {
  
  	public static void main(String[] args) throws Exception {
  
  		new Thread(null, new A(), "SwapnilGanguly", 1 << 24).start();
  	}
  
  	static class Pair {
  
  		long val;
  		int index;
  
  		Pair(long a, int b) {
  
  			val = a;
  			index = b;
  		}
  	}
  
  	public void run() {
  
  		SwapScanner sc = new SwapScanner();
  		PrintWriter pr = new PrintWriter(System.out);
  
  		int T = sc.nextInt();
  
  		while (T-- > 0) {
  
  			int n = sc.nextInt();
  			long ar[] = new long[n];
  			Pair[] p = new Pair[n];
  
  			for (int i = 0; i < n; i++) {
  
  				ar[i] = sc.nextLong();
  				p[i] = new Pair(ar[i], i);
  			}
  
  			long ans = 0;
  
  			for (int i = 0; i < n - 1; i++)
  				ans = Math.max(ans, ar[i] * ar[i + 1]);
  
  			pr.println(ans);
  		}
  
  		pr.close();
  	}
  
  	public static void sort(int[] a) {
  
  		ArrayList<Integer> l = new ArrayList<>();
  
  		for (int i : a)
  			l.add(i);
  
  		Collections.sort(l);
  
  		for (int i = 0; i < a.length; i++)
  			a[i] = l.get(i);
  	}
  
  	public static class SwapScanner {
  
  		BufferedReader br;
  		StringTokenizer st;
  
  		public SwapScanner() {
  
  			br = new BufferedReader(new InputStreamReader(System.in));
  		}
  
  		String next() {
  
  			while (st == null || !st.hasMoreElements()) {
  
  				try {
  
  					st = new StringTokenizer(br.readLine());
  				}
  
  				catch (IOException e) {
  
  					e.printStackTrace();
  				}
  			}
  
  			return st.nextToken();
  		}
  
  		int nextInt() {
  
  			return Integer.parseInt(next());
  		}
  
  		long nextLong() {
  
  			return Long.parseLong(next());
  		}
  
  		double nextDouble() {
  
  			return Double.parseDouble(next());
  		}
  
  		String nextLine() {
  
  			String str = "";
  
  			try {
  
  				str = br.readLine();
  			}
  
  			catch (IOException e) {
  
  				e.printStackTrace();
  			}
  
  			return str;
  		}
  
  		int[] readArray(int n) {
  
  			int[] ar = new int[n];
  
  			for (int i = 0; i < n; i++)
  				ar[i] = nextInt();
  
  			return ar;
  		}
  	}
  }