Buggy python submission (verdict: Time Limit Exceeded):
def z_algo(S):  # SとS[i:]の最長共通接頭辞 Z Algorithm
    N = len(S)
    A = [0] * N
    i = 1
    j = 0
    A[0] = l = len(S)
    while i < l:
        while i + j < l and S[j] == S[i + j]:
            j += 1
        if not j:
            i += 1
            continue
        A[i] = j
        k = 1
        while l-i > k < j - A[k]:
            A[i + k] = A[k]
            k += 1
        i += k
        j -= k
    return A


def resolve():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        a = z_algo(s[i:])
        for index, j in enumerate(a):
            if j <= index:
                ans = max(ans, j)
    print(ans)


if __name__ == '__main__':
    resolve()


Fixed submission:
def z_algo(S):
    N = len(S)
    A = [0] * N
    i = 1
    j = 0
    A[0] = l = len(S)
    while i < l:
        while i + j < l and S[j] == S[i + j]:
            j += 1
        if not j:
            i += 1
            continue
        A[i] = j
        k = 1
        while l-i > k < j - A[k]:
            A[i + k] = A[k]
            k += 1
        i += k
        j -= k
    return A


def resolve():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        a = z_algo(s[i:])
        for index, j in enumerate(a):
            if j <= index:
                ans = max(ans, j)
    print(ans)


if __name__ == '__main__':
    resolve()

Buggy python submission (verdict: Time Limit Exceeded):
def resolve():
    n = int(input())
    s = input()
    for i in range(n//2, 0, -1):
      for j in range(n-i):
        if s[j:j+i] in s[j+i:]:
          print(i)
          return
    print(0)


if __name__ == '__main__':
    resolve()

Fixed submission:
def z_algo(S):
    N = len(S)
    A = [0] * N
    i = 1
    j = 0
    A[0] = l = len(S)
    while i < l:
        while i + j < l and S[j] == S[i + j]:
            j += 1
        if not j:
            i += 1
            continue
        A[i] = j
        k = 1
        while l-i > k < j - A[k]:
            A[i + k] = A[k]
            k += 1
        i += k
        j -= k
    return A


def resolve():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        a = z_algo(s[i:])
        for index, j in enumerate(a):
            if j <= index:
                ans = max(ans, j)
    print(ans)


if __name__ == '__main__':
    resolve()

Buggy python submission (verdict: Time Limit Exceeded):
import re


def resolve():
    n = int(input())
    s = input()
    for i in range(n//2, 0, -1):
      for j in range(n-i):
        if re.search(s[j:j+i]+r".*"+s[j:j+i],s)!=None:
          print(i)
          return
    print(0)


if __name__ == '__main__':
    resolve()

Fixed submission:
def z_algo(S):
    N = len(S)
    A = [0] * N
    i = 1
    j = 0
    A[0] = l = len(S)
    while i < l:
        while i + j < l and S[j] == S[i + j]:
            j += 1
        if not j:
            i += 1
            continue
        A[i] = j
        k = 1
        while l-i > k < j - A[k]:
            A[i + k] = A[k]
            k += 1
        i += k
        j -= k
    return A


def resolve():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        a = z_algo(s[i:])
        for index, j in enumerate(a):
            if j <= index:
                ans = max(ans, j)
    print(ans)


if __name__ == '__main__':
    resolve()

Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter
import re


def resolve():
    n = int(input())
    s = input()
    for i in range(n // 2, 0, -1):
        c = Counter([s[x: x + i] for x in range(n - i + 1)])
        for j in c.most_common():
            if j[1] < 2:
                break
            if re.match(r"^.*" + j[0] + r".*" + j[0] + r".*$", s):
                print(i)
                return
    print(0)


if __name__ == '__main__':
    resolve()


Fixed submission:
def z_algo(S):
    N = len(S)
    A = [0] * N
    i = 1
    j = 0
    A[0] = l = len(S)
    while i < l:
        while i + j < l and S[j] == S[i + j]:
            j += 1
        if not j:
            i += 1
            continue
        A[i] = j
        k = 1
        while l-i > k < j - A[k]:
            A[i + k] = A[k]
            k += 1
        i += k
        j -= k
    return A


def resolve():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        a = z_algo(s[i:])
        for index, j in enumerate(a):
            if j <= index:
                ans = max(ans, j)
    print(ans)


if __name__ == '__main__':
    resolve()

Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter


def resolve():
    n = int(input())
    s = input()
    for i in range(n // 2, 0, -1):
        c = Counter([s[x:x + i] for x in range(n - i + 1)])
        for j in [x for x in c if c.get(x) > 1]:
            if j in s[s.find(j) + i:]:
                print(i)
                return
    print(0)


if __name__ == '__main__':
    resolve()

Fixed submission:
def z_algo(S):
    N = len(S)
    A = [0] * N
    i = 1
    j = 0
    A[0] = l = len(S)
    while i < l:
        while i + j < l and S[j] == S[i + j]:
            j += 1
        if not j:
            i += 1
            continue
        A[i] = j
        k = 1
        while l-i > k < j - A[k]:
            A[i + k] = A[k]
            k += 1
        i += k
        j -= k
    return A


def resolve():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        a = z_algo(s[i:])
        for index, j in enumerate(a):
            if j <= index:
                ans = max(ans, j)
    print(ans)


if __name__ == '__main__':
    resolve()