这个该怎么写呢？还要补充点啥？
n = eval(input())
with open('text.txt', 'r', encoding='utf8') as f:
mark=True
for i in range(n):
txt = f.readline().replace('\n', '')
if txt:
if "A" == txt[0]:
print(txt)
mark=False
if mark:
print("not found")