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

t = int(input())
for i in range(t):
    n = int(input())
    fish = list(map(int, input().split()))
    mx = max(fish)
    last_m = -1
    psbl = False
    for i in range(n):
        if fish[i] == mx:
            last_m = i
            if psbl:
                break
        else:
            psbl = True
            if last_m > -1:
                break
    if psbl:
        print(last_m + 1)
    else:
        print(-1)