def main():
    myList=[]
    choice = 0
    while choice !='4':
        choice= raw_input('1.add number to list\n2.get mean \n3.get median \n4.quit')
        if choice == '1':
            addNum(myList)
        if choice == '2':
            getMean(myList)
        if choice == '3':
            getMedian(myList)
        if int(choice) < 0:
            print "invalid input"
        if int(choice) > 4:
            print "invalid input"
##break
##input error messages
def addNum(myList):
    while True:
        num = raw_input("input new number:")
        try:
            num = int(num)
            if num < 0:
                raise ValueError
            break
        except:
            print"invalid input"
        
        
    myList.append(num)

def getMean(myList):
    total = 0.0
    for value in myList:
        total = total  + value
    mean = total/len(myList)
    print "the mean is:" , mean

def getMedian (myList):
    index= 2
    if len(myList)%2 == 0:
        myMed = (myList[index] + myList[myMed-1])/2
    else:
        myList[len(myList)/2]
    print myMed
        

##    mid = 2
##    prev = mid-1 
##    if len(myList)%2 == 0:
####        mid = 2
####        prev = mid-1
##        myMed=(myList[mid]+myList[prev])/2
##        print myMed
####    else myMed = [len(myList)/2]:
##        
main()