thing.py

import sys

chars = sorted(sys.stdin.read())[1:]
histogram = {}

for c in chars:
    if c in histogram:
        histogram[c] += 1
    else:
        histogram[c] = 1

flag = True
odd, even = 0, 0

for char, count in histogram.items():
    if count % 2 != 0:
        odd += 1
    else:
        even +=1

if len(chars) % 2 == 0:
    # check there is an even number of every character
    flag = odd == 0
else:
    if odd == 1:
        flag = True
    else:
        flag = False

print("YES" if flag else "NO")