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.util.StringTokenizer;
  
  public class Main {
  
      static long solve(int n, int[] arr) {
          long ret = 0;
  
          for (int i = 1; i < n; i++) {
              ret = Math.max(ret, (long) arr[i - 1] * arr[i]);
          }
  
          return ret;
      }
  
      public static void main(String[] args) throws IOException {
  //        System.out.println("===== input =====");
  //        BufferedReader br = new BufferedReader(new FileReader("input/input1.txt"));
  //        BufferedReader br2 = new BufferedReader(new FileReader("input/input1.txt"));
  //        String s;
  //        while ((s = br2.readLine()) != null) {
  //            System.out.println(s);
  //        }
  //        System.out.println("===== output =====");
           BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st = new StringTokenizer(br.readLine());
          StringBuilder out = new StringBuilder();
          int T = Integer.parseInt(st.nextToken());
          while (T-- > 0) {
              int N = Integer.parseInt(br.readLine());
              int[] arr = new int[N];
  
              st = new StringTokenizer(br.readLine());
              for (int i = 0; i < N; i++) {
                  arr[i] = Integer.parseInt(st.nextToken());
              }
  
              out.append(solve(N, arr)).append("\n");
          }
          System.out.println(out);
      }
  }