1
for i in range(1, 51):
if i % 2 ==0:
print(i, '天天向上')
else:
print(i, '好好学习')
print('好好学习、天天向上')
2
s = input()
r = ''
for t in s[::-1]:
if t.isdigit():
r += t
if r:
print(r)
else:
print('字符串中没有数字字符')
#1
for i in range(1,51):
print(i,end='')
if i%2:
print('好好学习')
else:
print('天天向上')
print('好好学习,天天向上')
#2
n=input()[::-1]
a=0
for i in n:
if i.isdigit():
print(i,end='')
a=1
if not a:
print('字符串中没有数字字符')