input_line = input()
words = list(input_line)
if len(words) % 2 == 1:
    print('NO')
else:
    word1 = []
    word2 = []
    for n in range(len(words)/2 + 1):
        word1.append(words[n-1])
    for n in range(len(words)/2 + 1):
        word2.append(words[n + (len(words)/2) - 1])
    if word1 == word2:
        print('YES')
    else:
        print('NO')