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

def inp():
    return int(input())
def inl():
    return [int(i) for i in input().split()]

if __name__ == "__main__":
    p = inp()
    for _ in range(p):
        n = inp()
        x = inl()
        max_item = max(x)
        cnt = -1
        for i in range(n):
            if x[i] == max_item:
                if i<n-1 and x[i+1]<max_item:
                    cnt = i+1
                    break
                elif i>0 and x[i-1]<max_item:
                    cnt = i+1
                    break
        print(cnt)