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: //credit for scanner https://gist.github.com/alsuga/85ff07d7a080ec06c762
  import java.io.*;
  import java.util.*;
  
  public class MyClass {
      public static void main(String[] args) throws IOException {
          Scanner sc = new Scanner(System.in);
          for(int t = sc.nextInt(); t > 0; t--){
              int n = sc.nextInt();
              long[] a = new long[n];
              for(int i = 0; i < n; i++){
                  a[i] = (long)sc.nextLong();
              }
              long solution = 0;
              for(int i = 1; i < a.length; i++){
                  solution = Math.max(solution, a[i-1] * a[i]);
              }
              System.out.println(solution);
          }
      }
  }
  class Scanner {
      public BufferedReader reader;
      public StringTokenizer st;
  
      public Scanner(InputStream stream) {
          reader = new BufferedReader(new InputStreamReader(stream));
          st = null;
      }
  
      public String nextLine() {
          while (st == null || !st.hasMoreTokens()) {
              try {
                  String line = reader.readLine();
                  if (line == null) return null;
                  st = new StringTokenizer(line);
              } catch (Exception e) {
                  throw (new RuntimeException());
              }
          }
          String ret = "";
          while (st.hasMoreTokens()) {
              String curr = st.nextToken();
              ret += curr + (st.hasMoreTokens() ? " " : "");
          }
          return ret;
      }
  
      public boolean hasNext(){
          return st.hasMoreTokens();
      }
  
      public String next() {
          while (st == null || !st.hasMoreTokens()) {
              try {
                  String line = reader.readLine();
                  if (line == null) return null;
                  st = new StringTokenizer(line);
              } catch (Exception e) {
                  throw (new RuntimeException());
              }
          }
          return st.nextToken();
      }
  
      public int nextInt() {
          return Integer.parseInt(next());
      }
      public long nextLong() {
          return Long.parseLong(next());
      }
      public double nextDouble() {
          return Double.parseDouble(next());
      }
  }