Buggy python submission (verdict: Time Limit Exceeded):
 #ランレングス圧縮とは RLE(Run Length Encoding)とも言われます。
#連続したデータを、ひとつ分のデータと連続した長さで表現します。
def rle(s):
    tmp, count, ans_c,ans_n = int(s[0]),1,[] , []
    for i in range(1,len(s)):
        if tmp == int(s[i]):
            count += 1
        else:
            ans_c.append(tmp)
            ans_n.append(count)
            tmp = int(s[i])
            count = 1
    ans_c.append(tmp)
    ans_n.append(count)
    return ans_c,ans_n

   # AAABBCCCCA ⇒ A3B2C4A1

# 初期入力
import sys
input = sys.stdin.readline
N,K = (int(x) for x in input().split())
S =input().strip()

#0と1が何回続くか
a_c,a_n =rle(S)
a_len =len(a_c)
count =[0]*a_len
ans =0
if a_c[-1] ==1:
    f=1 
if a_c[-1] ==0:
    f=0 

if K >= (a_len +1)//2:
    ans =N
elif a_len==2:
    ans =N
elif a_len ==3 and a_c[0]==1:
    ans=N
else:
    if a_c[0] ==1:
        i=0
        while not(i +2*K +1 ==a_len+2 or i +2*K +1 ==a_len+3):
            count[i] =sum(a_n[i:i+2*K +1])
            i +=2
    else:
        count[0] =sum(a_n[:2*K])
        i=1
        while not(i +2*K +1 ==a_len +2 or i +2*K +1 == a_len +3):
            count[i] =sum(a_n[i:i+2*K+1])
            i +=2      

    ans =max(count)
print(ans)

Fixed submission:
 #ランレングス圧縮とは RLE(Run Length Encoding)とも言われます。
#連続したデータを、ひとつ分のデータと連続した長さで表現します。
def rle(s):
    tmp, count, ans_c,ans_n = int(s[0]),1,[] , []
    for i in range(1,len(s)):
        if tmp == int(s[i]):
            count += 1
        else:
            ans_c.append(tmp)
            ans_n.append(count)
            tmp = int(s[i])
            count = 1
    ans_c.append(tmp)
    ans_n.append(count)
    return ans_c,ans_n

# 初期入力
import sys
input = sys.stdin.readline
N,K = (int(x) for x in input().split())
S =input().strip()

#0と1が何回続くか
a_c,a_n =rle(S)
a_len =len(a_c)
a_n +=[0]
count =[0]*a_len
ans =0

#
if K >= (a_len +1)//2:
    ans =N
elif a_len==2:
    ans =N
elif a_len ==3 and a_c[0]==1:
    ans=N
else:
    if a_c[0] ==1:
        i=2
        indx =i +2*K 
        count[0] =sum(a_n[:0 +2*K +1])
        while not(indx ==a_len+2 or indx ==a_len+1):
            count[i] =count[i-2] -a_n[i-2] -a_n[i-1] + a_n[indx-1] +a_n[indx]
            i +=2
            indx =i +2*K 
    else:
        count[0] =sum(a_n[:2*K])
        count[1] =sum(a_n[1: 1+2*K+1])
        i=3
        indx =i +2*K 
        while not(indx ==a_len+2 or indx ==a_len+1):
            count[i] =count[i-2] -a_n[i-2] -a_n[i-1] + a_n[indx-1] +a_n[indx]
            i +=2      
            indx =i +2*K 
    ans =max(count)
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
 #ランレングス圧縮とは RLE(Run Length Encoding)とも言われます。
#連続したデータを、ひとつ分のデータと連続した長さで表現します。
def rle(s):
    tmp, count, ans = s[0], 1, []
    for i in range(1,len(s)):
        if tmp == s[i]:
            count += 1
        else:
            ans.append((tmp,count))
            tmp = s[i]
            count = 1
    ans.append((tmp,count))
    return ans

   # AAABBCCCCA ⇒ A3B2C4A1

# 初期入力
import sys
input = sys.stdin.readline
N,K = (int(x) for x in input().split())
S =input().strip()

#0と1が何回続くか
a =rle(S)
a_len =len(a)
count =[0]*a_len
ans =0

if K >= (a_len +1)//2:
    ans =N
else:
    for i in range(a_len):
        j =0
        count_0 =0
        while count_0 <K and i+j <a_len: #and j <a_len:
            count[i] +=a[i+j][1]
            if a[i+j][0]=="0":
                count_0 +=1
                if count_0 ==K and i+j+1 <a_len :
                    count[i] +=a[i+j+1][1]
            j +=1
    ans =max(count)
print(ans)

Fixed submission:
 #ランレングス圧縮とは RLE(Run Length Encoding)とも言われます。
#連続したデータを、ひとつ分のデータと連続した長さで表現します。
def rle(s):
    tmp, count, ans_c,ans_n = int(s[0]),1,[] , []
    for i in range(1,len(s)):
        if tmp == int(s[i]):
            count += 1
        else:
            ans_c.append(tmp)
            ans_n.append(count)
            tmp = int(s[i])
            count = 1
    ans_c.append(tmp)
    ans_n.append(count)
    return ans_c,ans_n

# 初期入力
import sys
input = sys.stdin.readline
N,K = (int(x) for x in input().split())
S =input().strip()

#0と1が何回続くか
a_c,a_n =rle(S)
a_len =len(a_c)
a_n +=[0]
count =[0]*a_len
ans =0

#
if K >= (a_len +1)//2:
    ans =N
elif a_len==2:
    ans =N
elif a_len ==3 and a_c[0]==1:
    ans=N
else:
    if a_c[0] ==1:
        i=2
        indx =i +2*K 
        count[0] =sum(a_n[:0 +2*K +1])
        while not(indx ==a_len+2 or indx ==a_len+1):
            count[i] =count[i-2] -a_n[i-2] -a_n[i-1] + a_n[indx-1] +a_n[indx]
            i +=2
            indx =i +2*K 
    else:
        count[0] =sum(a_n[:2*K])
        count[1] =sum(a_n[1: 1+2*K+1])
        i=3
        indx =i +2*K 
        while not(indx ==a_len+2 or indx ==a_len+1):
            count[i] =count[i-2] -a_n[i-2] -a_n[i-1] + a_n[indx-1] +a_n[indx]
            i +=2      
            indx =i +2*K 
    ans =max(count)
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
 #ランレングス圧縮とは RLE(Run Length Encoding)とも言われます。
#連続したデータを、ひとつ分のデータと連続した長さで表現します。
def rle(s):
    tmp, count, ans = s[0], 1, []
    for i in range(1,len(s)):
        if tmp == s[i]:
            count += 1
        else:
            ans.append((tmp,count))
            tmp = s[i]
            count = 1
    ans.append((tmp,count))
    return ans

   # AAABBCCCCA ⇒ A3B2C4A1

# 初期入力
import sys
input = sys.stdin.readline
N,K = (int(x) for x in input().split())
S =input().strip()

#0と1が何回続くか
a =rle(S)
a_len =len(a)
count =[0]*a_len
ans =0

if K >= (a_len +1)//2:
    ans =N
else:
    for i in range(a_len):
        j =0
        count_0 =0
        while count_0 <K and i+j <a_len and j <a_len:
            count[i] +=a[i+j][1]
            if a[i+j][0]=="0":
                count_0 +=1
                if count_0 ==K and i+j+1 <a_len :
                    count[i] +=a[i+j+1][1]
            j +=1
    ans =max(count)
print(ans)

Fixed submission:
 #ランレングス圧縮とは RLE(Run Length Encoding)とも言われます。
#連続したデータを、ひとつ分のデータと連続した長さで表現します。
def rle(s):
    tmp, count, ans_c,ans_n = int(s[0]),1,[] , []
    for i in range(1,len(s)):
        if tmp == int(s[i]):
            count += 1
        else:
            ans_c.append(tmp)
            ans_n.append(count)
            tmp = int(s[i])
            count = 1
    ans_c.append(tmp)
    ans_n.append(count)
    return ans_c,ans_n

# 初期入力
import sys
input = sys.stdin.readline
N,K = (int(x) for x in input().split())
S =input().strip()

#0と1が何回続くか
a_c,a_n =rle(S)
a_len =len(a_c)
a_n +=[0]
count =[0]*a_len
ans =0

#
if K >= (a_len +1)//2:
    ans =N
elif a_len==2:
    ans =N
elif a_len ==3 and a_c[0]==1:
    ans=N
else:
    if a_c[0] ==1:
        i=2
        indx =i +2*K 
        count[0] =sum(a_n[:0 +2*K +1])
        while not(indx ==a_len+2 or indx ==a_len+1):
            count[i] =count[i-2] -a_n[i-2] -a_n[i-1] + a_n[indx-1] +a_n[indx]
            i +=2
            indx =i +2*K 
    else:
        count[0] =sum(a_n[:2*K])
        count[1] =sum(a_n[1: 1+2*K+1])
        i=3
        indx =i +2*K 
        while not(indx ==a_len+2 or indx ==a_len+1):
            count[i] =count[i-2] -a_n[i-2] -a_n[i-1] + a_n[indx-1] +a_n[indx]
            i +=2      
            indx =i +2*K 
    ans =max(count)
print(ans)