1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Task1433C {

  public static void main(String[] args) throws IOException {
    Scanner scanner = new Scanner(System.in);

    StringBuilder result = new StringBuilder();



    int t = scanner.nextInt();

    long[][] globalMass = new long[t][];

    for (int i = 0; i < t; i++) {
      long n = scanner.nextLong();

      long[] mass = new long[(int) n];
      for (long l = 0; l < n; l++) {
        mass[(int) l] = scanner.nextLong();
      }
      globalMass[i] = mass;

    }

    for (int i = 0; i < globalMass.length; i++) {
      solveTask(globalMass[i]);
    }


    System.out.println(result.toString().trim());
  }


  public static String solveTask(long[] mass) {

    List<Long> longs = new ArrayList<>();
    for (long l : mass) {
      longs.add(l);
    }

    Long max = Collections.max(longs);
    int countSame = 0;
    for (long l : mass) {
      if (l == max)
        countSame++;
    }

    if(countSame == mass.length){
      System.out.println("-1");
      return "";
    }

    int maxPosition = 0;
    for (int i = 0; i < mass.length; i++) {
      if(mass[i] == max)
        maxPosition = i;
    }

    System.out.println(maxPosition + 1);

    return String.valueOf("");
  }

}