from collections import Counter

s = input()

c = Counter(s)

if len(c.values()) == 1:
    if len(s) == 1:
        ans = "YES"
    else:
        ans = "NO"

elif len(c.values()) == 2:
    if len(s) == 2:
        ans = "YES"
    else:
        ans = "NO"

else:
    cnt = sorted(c.values())
    bl1 = cnt[0] == cnt[1] == cnt[2]
    bl2 = cnt[0] == cnt[1] == cnt[2] - 1
    bl3 = cnt[0] == cnt[1] - 1 == cnt[2] - 1
    if bl1 or bl2 or bl3:
        ans = "YES"
    else:
        ans = "NO"

print(ans)
