computer second-level prictices

Use function ebal() get a simple calculate.
`#simple calculate
n=eval(input('please input a expression:'))
print(n)
`

- lecture 3 practices

`#get more than 100 digits
n=eval(input('please input a number bigger than 100:'))
n2=n/100
n3=round(n2,0)
if n2<n3 :
    n3=int(n3)-1
else:
    n3=int(n3)
print(n3)`

