Problem:
We have an H-by-W matrix. Let a_{ij} be the element at the i-th row from the top and j-th column from the left. In this matrix, each a_{ij} is a lowercase English letter.  Snuke is creating another H-by-W matrix, A', by freely rearranging the elements in A. Here, he wants to satisfy the following condition:    * Every row and column in A' can be read as a palindrome.  Determine whether he can create a matrix satisfying the condition.

Incorrect submission (verdict: Wrong Answer):
import sys
stdin = sys.stdin

def li(): return map(int, stdin.readline().split())
def li_(): return map(lambda x: int(x)-1, stdin.readline().split())
def lf(): return map(float, stdin.readline().split())
def ls(): return stdin.readline().split()
def ns(): return stdin.readline().rstrip()
def lc(): return list(ns())
def ni(): return int(stdin.readline())
def nf(): return float(stdin.readline())

from collections import Counter

h,w = li()

cnt = Counter([])
for _ in range(h):
    tmp = lc()
    for c in tmp:
        cnt[c] += 1

print(cnt)
exist = True

if h%2 == 0 and w%2 == 0:
    for key,value in cnt.items():
        if value%4 != 0:
            exist = False
            break
        
elif h%2 == 1 and w%2 == 1:
    odd = 0
    mod4_2 = 0
    for key,value in cnt.items():
        if value % 2 == 1:
            odd += 1
        elif value % 4 == 2:
            mod4_2 += 1
            
    if odd > 1:
        exist = False
    elif mod4_2 > (h+w-2)//2:
        exist = False
        
else:
    odmax = 0
    if h%2 == 0:
        odmax = h//2
    else:
        odmax = w//2
        
    
    mod4_2 = 0
    for key, value in cnt.items():
        if value%2 != 0:
            exist = False
            break
        elif value%4 == 2:
            mod4_2 +=1
            
    if mod4_2 > odmax:
        exist = False
        
        
if exist:
    print("Yes")
else:
    print("No")

Fixed, accepted submission:
import sys
stdin = sys.stdin

sys.setrecursionlimit(10 ** 7)

def li(): return map(int, stdin.readline().split())
def li_(): return map(lambda x: int(x) - 1, stdin.readline().split())
def lf(): return map(float, stdin.readline().split())
def ls(): return stdin.readline().split()
def ns(): return stdin.readline().rstrip()
def lc(): return list(ns())
def ni(): return int(stdin.readline())
def nf(): return float(stdin.readline())

from collections import defaultdict

def judge(cnts, h, w):
    odd_cnt = 0
    mod4_2_cnt = 0
    mod4_0_cnt = 0

    for key, val in cnts.items():
        if val % 2 == 1:
            odd_cnt += 1

        elif val % 4 == 2:
            mod4_2_cnt += 1

        else:
            mod4_0_cnt += 1


    if h == 1 and w == 1:
        return True

    elif h == 1:
        if w % 2 == 1:
            return True if odd_cnt == 1 else False
        else:
            return True if odd_cnt == 0 else False

    elif w == 1:
        if h % 2 == 1:
            return True if odd_cnt == 1 else False
        else:
            return True if odd_cnt == 0 else False

    elif h % 2 == 1 and w % 2 == 1:
        return True if mod4_2_cnt == (w//2 + h//2) and odd_cnt == 1 else False

    elif h%2 == 1:
        return True if mod4_2_cnt == (w//2) and odd_cnt == 0 else False

    elif w%2 == 1:
        return True if mod4_2_cnt == (h//2) and odd_cnt == 0 else False

    else:
        return True if mod4_2_cnt == 0 and odd_cnt == 0 else False


h, w = li()
a = [ns() for _ in range(h)]

char_cnt = defaultdict(int)

for ai in a:
    for aij in ai:
        char_cnt[aij] += 1

print("Yes" if judge(char_cnt, h, w) else "No")