import java.util.Scanner; // 注意类名必须为 Main, 不要有任何 package xxx 信息 public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); // 注意 hasNext 和 hasNextLine 的区别 while (in.hasNextInt()) { // 注意 while 处理多个 case int T = in.nextInt(); while (T-- > 0) { int n = in.nextInt(); int moreThen2Count = 0; int maxCount = 0; for (int i=0;i<n;i++) { int v = in.nextInt(); if (v > 1) { moreThen2Count++; } maxCount = Math.max(maxCount, v); } if (n == 1) { System.out.println(-1); } else if (moreThen2Count > 1) { System.out.println(maxCount); } else { System.out.println(maxCount-1); } } } } }