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())
    f = list(map(int, input().split()))
    maxF = max(f)
    minF = min(f)
    if maxF == minF:
        print(-1)
    else:
        for j in range(n):
            if f[j] == maxF:
                if (j > 0 and f[j] > f[j-1]) or (j < n-1 and f[j] > f[j+1]):
                    domF = j
        print(domF+1)
