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