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 tc in range(t):
    n = int(input())
    arr = list(map(int, input().split()))
    mx = 0
    mn = 10**10
    for p in arr:
        mx = max(mx, p)
        mn = min(mn, p)
    if mx == mn:
        mx += 1
    ans = -1
    for i in range(n):
        if arr[i] == mx:
            if (i > 0 and arr[i-1] < mx) or (i < n-1 and arr[i+1] < mx):
                ans = i+1
                break
    print(ans)
