# cook your dish here
n = int(input())
substrings = []
def palindrome(n):
s = input().split()[0]
for i in range(n):
j = i + 1
while j <= n:
substrings.append(s[i:j])
j += 1
uniqueSubstrings = list(set(substrings))
notPalindromes = set()
for i in range(len(uniqueSubstrings)):
substring = uniqueSubstrings[i]
for j in range(len(substring)):
if substring[len(substring) - (j + 1)] != substring[j]:
notPalindromes.add(substring)
palindromes = sorted(list(set(uniqueSubstrings) - notPalindromes))
addPalindromes(palindromes)
def addPalindromes(palindromes):
T = ''.join(palindromes)
main(T)
def main(T):
m = int(input())
for i in range(m):
L, R = map(int, input().split())
print(T[L - 1: R]) if R - 1 <= len(T) else print(-1)
palindrome(n)
It gives correct answer with given sample inputs and custom inputs, but in submission it cant pass any test case. Thanks in advance.