题解 | #DNA序列#

gene , l , rate = input() , int(input()) , []
for i in range(len(gene)):
    rate.append(gene[i:min(i+l,len(gene))].count('C')+gene[i:min(i+l,len(gene))].count('G'))
print(gene[rate.index(max(rate)):rate.index(max(rate))+l])
#相对会耗时但很简短能过