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())
import array as arr
ans = arr.array('i',[0]*t)

for i in range(t):
    n = int(input())
    x = arr.array('i',list(map(int,input().split())))
    xm = max(x)
    xmin = min(x)
    im = x.index(xm)
    if xmin == xm:
        ans[i] = -1
    elif im!=0:
        ans[i] = im+1
    else:
        while x[im+1]==xm:
            im += 1
        ans[i] = im+1
for i in ans:
    print(i)
