import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
eps = 1.0 / 10**15
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
def pf(s): return print(s, flush=True)


def main():
    s = S()
    c = collections.Counter(s)
    if len(c) == 1:
        if len(s) == 1:
            return 'YES'
        return 'NO'
    if len(c) == 2:
        if len(s) <= 2:
            return 'YES'
        return 'NO'
    if max(c.values()) - min(c.values()) <= 1:
        return 'YES'

    return 'NO'



print(main())


