题解 | #DNA序列#
DNA序列
https://www.nowcoder.com/practice/e8480ed7501640709354db1cc4ffd42a
s = input()
n = int(input())
count = 0
first = ''
for i in range(len(s)-n+1):
ss = s[i:i+n]
if 'C' in ss and 'G' in ss and ss.count('C')+ss.count('G')>count:
count = ss.count('C')+ss.count('G')
first = ss
print(first)
