题解 | #DNA序列#
DNA序列
http://www.nowcoder.com/practice/e8480ed7501640709354db1cc4ffd42a
tes=input()
n=int(input())
c=0
t=''
for i in range(len(tes)-n+1):
a=tes[i:i+n]
b=0
for s in range(n):
if a[s]=='G' or a[s]=='C':
b+=1
if b>c:
c=b
t=a
print(t)