题解 | #分苹果#

import sys

data=sys.stdin.readlines()

data[1]=data[1].strip(" ")
m=data[1].split(" ")

if '\n' in m:
    m.remove('\n')

def jox(l):
    val=l[0]%2
    for item in l:
        if item%2!=val:
            return False
    return True



for i in range(len(m)):
    m[i]=m[i].strip("\n")
    m[i]=int(m[i])

avg=int(sum(m)/len(m))

if float(int(sum(m)/len(m)))!=sum(m)/len(m) or jox(m)==False :
    print(-1)
else:

    count=0
    for item in m:
        if item>avg:
            count=count+int((item-avg)/2)

    print(count)