import collections

def gameOfThrones(s):
    d = collections.Counter(s)
    multipleOddVal = False
    
    for val in d.values():
        if (val % 2 == 1):
            if (multipleOddVal):
                return "NO"
                break
            else:
                multipleOddVal = True
    else:
        return "YES"

s = input()

result = gameOfThrones(s)

print(result)