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 _ in range(t):
    n = int(input())
    a = list(map(int, input().split()))
    M = max(a)
    ans = -1
    
    for i in range(n):
        if a[i]==M:
            flag = False
            
            if i-1>=0 and a[i]>a[i-1]:
                flag = True
            
            if i+1<n and a[i]>a[i+1]:
                flag = True
            
            if flag:
                ans = i+1
    
    print(ans)