def bound_solid(i,j):
if (i-1)>=0:
l=(i-1)
else:
l=n-1
if (i+1)<=n-1:
u=(i+1)
else:
u=0
return(l,u)
T=input()#the error is at this line
T=int(T)
for i in range (T):
n=int(input())
atk=list(map(int,input().split(" “)))
defn=list(map(int,input().split(” ")))
max_defns=0
for j in range(n):
l,u=bound_solid(j,n)
if(defn[j]>(atk[l]+atk[u])):
if(defn[j]>max_defns):
max_defns=defn[j]
if(max_defns>0):
print(max_defns)
else:
print(-1)