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.util.*;
import java.util.Map.Entry;


import java.io.*;
import java.math.BigInteger;
 
 
public class Main {
	
	public static void main(String[] args) throws IOException {
		int t=sc.nextInt();
		out:while(t-->0) {
			int x=sc.nextInt();
			int [] arr=sc.nextIntArray(x);
			for(int i=1;i<x;i++) {
				if(arr[i]>arr[i-1]) {
					pw.println(i+1);
					continue out;
				}else if(arr[i]<arr[i-1]) {
					pw.println(i);
					continue out;
				}
			}
			pw.println(-1);
		}
		pw.flush();
		pw.close();
	}
	 static long gcd(long a, long b)
	    {
	      if (b == 0)
	        return a;
	      return gcd(b, a % b); 
	    }
	     
	static class pair implements Comparable <pair>{
		double c,r;
		public pair(double c,double r) {this.c=c; this.r=r;}
		
		public int compareTo(pair o) {
			return Double.compare(c+r*o.c,o.c+o.r*c);
		}
		
	}
    static class Scanner {
    	 
        private InputStream in;
        private byte[] buffer = new byte[1024];
        private int curbuf;
        private int lenbuf;
 
        public Scanner(InputStream in) {
            this.in = in;
            this.curbuf = this.lenbuf = 0;
        }
 
        public boolean hasNextByte() {
            if (curbuf >= lenbuf) {
                curbuf = 0;
                try {
                    lenbuf = in.read(buffer);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (lenbuf <= 0)
                    return false;
            }
            return true;
        }
 
        private int readByte() {
            if (hasNextByte())
                return buffer[curbuf++];
            else
                return -1;
        }
 
        private boolean isSpaceChar(int c) {
            return !(c >= 33 && c <= 126);
        }
 
        private void skip() {
            while (hasNextByte() && isSpaceChar(buffer[curbuf]))
                curbuf++;
        }
 
        public boolean hasNext() {
            skip();
            return hasNextByte();
        }
 
        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (!isSpaceChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }
 
        public int nextInt() {
            if (!hasNext())
                throw new NoSuchElementException();
            int c = readByte();
            while (isSpaceChar(c))
                c = readByte();
            boolean minus = false;
            if (c == '-') {
                minus = true;
                c = readByte();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res = res * 10 + c - '0';
                c = readByte();
            } while (!isSpaceChar(c));
            return (minus) ? -res : res;
        }
 
        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            int c = readByte();
            while (isSpaceChar(c))
                c = readByte();
            boolean minus = false;
            if (c == '-') {
                minus = true;
                c = readByte();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res = res * 10 + c - '0';
                c = readByte();
            } while (!isSpaceChar(c));
            return (minus) ? -res : res;
        }
 
        public double nextDouble() {
            return Double.parseDouble(next());
        }
 
        public int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }
        public Integer [] sortedIntArray(int n) {
        	Integer[] a = new Integer[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            Arrays.sort(a);
            return a;
        }
        public Long [] sortedLongArray(int n) {
        	Long[] a = new Long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            Arrays.sort(a);
            return a;
        }
 
        public long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }
 
    }
	static Scanner sc = new Scanner(System.in);
	static PrintWriter pw = new PrintWriter(System.out);
}