def erfenchaozhao(n,shu):
    head=0
    tail=len(n)-1
    while head<=tail:
        mid=(head+tail)//2
        caishu=n[mid]
        if shu==caishu:
            return mid
        elif shu>caishu:
            head=mid+1
        elif shu<caishu:
            tail=mid-1
    return False
num=[1,2,3,4,5,6,7,8,9]
shui=int(input("请输入一个数:"))

if erfenchaozhao(num,shui):
    print(f"{shui}在这个列表中")
else:
    print(f"{shui}不在这个列表中")