def erfenchazhao(n,shu):
    length=len(n)
    low=1
    high=length-1
    while low<=high:
        mid=(low+high)//2
        caishu=n[mid]
        if shu==caishu:
            return mid
        elif shu<caishu:
            high=mid-1
        elif shu>caishu:
            low=mid+1
    return False
n=[1,2,3,4,5,6,7,8,9]
shu=int(input("请输入数"))
if erfenchazhao(n,shu):
    print("数在这个列表中")
else:
    print('数不在这个列表中')