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 sys
input = sys.stdin.readline

t=int(input())
for tests in range(t):
    n=int(input())
    A=list(map(int,input().split()))

    MAX=max(A)

    for i in range(n):
        if A[i]==MAX:
            if i>0 and A[i]>A[i-1]:
                print(i+1)
                break
            if i<n-1 and A[i]>A[i+1]:
                print(i+1)
                break
    else:
        print(-1)

