# https://atcoder.jp/contests/cf17-final-open/tasks/cf17_final_b
from collections import Counter

S = input()
counter = Counter(S)
most_common = list(counter.items())
while len(most_common) < 3:
    most_common.append(('x', 0))
    
most_common.sort(key=lambda x:x[1] ,reverse=False)
# print(most_common)
ret = 'YES' if most_common[1][1] <= most_common[0][1]+1 and most_common[2][1] <= most_common[0][1]+1 else 'NO'
print(ret)