不知道为什么通不过呢
def exchange(num):
    if num==1:
        return 0
    else:
        if num%2==0:
            return int(num/2)
        else:
            return int((num-1)/2)

while True:
    try:
        a=1
        line=[]
        while(a!=0):
            a=int(input())
            if a==0:
                break
            else:
                line.append(a)
        for i in range(len(line)):
            print(exchange(line[i]))
    except:
        break