def ok():
    print("Yes")
    exit()

def ng():
    print("NO")
    exit()


try:
    x = input()
except:
    x = ''
n = len(x)


def check(a, b):
    for c in a + b[1::2]:
        b = b.replace(c, ' ')
    return ' ' not in b[::2]
        

for i in range(n):
    for j in range(i + 2, n+1):
        if check(x[:i] + x[j:], x[i:j]):ok()

ng()