# 1번
def solution(A):
    for num in A:
        if A.count(num) > (len(A)//2):
            return A.index(num)
    return None



# 2번
def palindrome(string):
    ls = []
    for i in range(len(string)):
        if string[i].isalpha():
            ls.append(string[i])

    for i in range(len(ls)):
        if ls[i] != ls[-(i+1)]:
            return False
    return True

print(palindrome("ABBA"))
print(palindrome("ABBAC"))
print(palindrome("ABB#A"))
print(palindrome("ABB#C"))