def diff(mylist):
    return max(mylist) - min(mylist)

def mean(mylist):
    return sum1(mylist)/len(mylist)

def sum1(mylist):
    acc = 0
    for item in mylist:
        acc = acc + item
    return acc

def sum2(mylist):
    acc = 0
    for index in range(len(mylist)):
        acc = acc + mylist[index]
    return acc

def median(mylist):
    copylist = mylist[:]
    copylist.sort()
    if len(copylist)%2 == 0:  # even
        rightmid = len(copylist)//2
        leftmid = rightmid-1
        result = (copylist[leftmid] + copylist[rightmid]) / 2.0
    else:
        mid = len(copylist)//2
        result = copylist[mid]
    return result