改成 只能往相鄰移動的話難度會增加

n=int(input())
num=[int(c) for c in input().split()]
if sum(num)%n !=0:
    print(-1)
else: 
    target=sum(num)//n
    flag =0 if target%2==0 else 1
    count=0
    for n in num:
        if n%2==flag:
            if n < target:
                count+=(target-n)//2
        else:
 

            print(-1)
            flag=2
            break
    if flag !=2: print(count)