# Game of thrones

got = input()
occ_table = {}
for i in got:
    if i not in occ_table:
        occ_table[i] = 1
    else:
        occ_table[i] += 1
unpaired_chars = 0
for i in occ_table.keys():
    if occ_table[i] % 2 is 1:
        unpaired_chars += 1
if unpaired_chars > 1:
    print("NO")
else:
    print("YES")
