Python if控制流语句

#!/usr/bin/env python
# -*- coding:utf-8 -*-

# Python if控制流语句
letter = input("please input:")

if letter == 'S':
    print('please input second letter:')
    letter = input("please input:")
    if letter == 'a':
        print('Saturday')
    elif letter == 'u':
        print('Sunday')
    else:
        print('data error')

elif letter == 'F':
    print('Friday')

elif letter == 'M':
    print('Monday')

elif letter == 'T':
    print('please input second letter')
    letter = input("please input:")

    if letter == 'u':
        print('Tuesday')
    elif letter == 'h':
        print('Thursday')
    else:
        print('data error')

elif letter == 'W':
    print('Wednesday')
else:
    print('data error')