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):
H, W = map(int, input().split())
A = []
for i in range(H):
    A.extend(list(input()))
A.sort()
print(A)
a = [0, 0, 0]
if H % 2 != 0 and W % 2 != 0:
    a[0] = 1
    a[1] = int(H / 2) + int(W / 2)
    a[2] = int((H * W - a[0] - a[1]) / 4)
elif H % 2 != 0:
    a[0] = 0
    a[1] = int(W / 2)
    a[2] = int((H * W - a[0] - a[1]) / 4)
elif W % 2 != 0:
    a[0] = 0
    a[1] = int(H / 2)
    a[2] = int((H * W - a[0] - a[1]) / 4)
else:
    a[0] = 0
    a[1] = 0
    a[2] = int(H * W / 4)
c = 1
cnt = [0, 0, 0]
for i in range(1, H * W):
    if A[i] == A[i - 1]:
        c += 1
    else:
        if c == 1:
            cnt[0] += 1
        elif c == 2:
            cnt[1] += 1
        elif c == 3:
            cnt[0] += 1
            cnt[1] += 1
        elif c == 4:
            cnt[2] += 1
        elif c > 4:
            cnt[2] += int(c / 4)
            c %= 4
            if c == 3:
                cnt[0] += 1
                cnt[1] += 1
            if c == 2:
                cnt[1] += 1
        c = 1
        
if c == 1:
    cnt[0] += 1
elif c == 2:
    cnt[1] += 1
elif c == 3:
    cnt[0] += 1
    cnt[1] += 1
elif c == 4:
    cnt[2] += 1
elif c > 4:
    cnt[2] += int(c / 4)
    c %= 4
    if c == 3:
        cnt[0] += 1
        cnt[1] += 1
    if c == 2:
        cnt[1] += 1

if a == cnt:
    print("Yes")
else:
    print("No")
    

Fixed, accepted submission:
H, W = map(int, input().split())
A = []
for i in range(H):
    A.extend(list(input()))
A.sort()
a = [0, 0, 0]
if H % 2 != 0 and W % 2 != 0:
    a[0] = 1
    a[1] = int(H / 2) + int(W / 2)
    a[2] = int((H * W - a[0] - a[1] * 2) / 4)
elif H % 2 != 0:
    a[0] = 0
    a[1] = int(W / 2)
    a[2] = int((H * W - a[0] - a[1] * 2) / 4)
elif W % 2 != 0:
    a[0] = 0
    a[1] = int(H / 2)
    a[2] = int((H * W - a[0] - a[1] * 2) / 4)
else:
    a[0] = 0
    a[1] = 0
    a[2] = int(H * W / 4)
c = 1
cnt = [0, 0, 0]
for i in range(1, H * W):
    if A[i] == A[i - 1]:
        c += 1
    else:
        if c == 1:
            cnt[0] += 1
        elif c == 2:
            cnt[1] += 1
        elif c == 3:
            cnt[0] += 1
            cnt[1] += 1
        elif c == 4:
            cnt[2] += 1
        elif c > 4:
            cnt[2] += int(c / 4)
            c %= 4
            if c == 3:
                cnt[0] += 1
                cnt[1] += 1
            if c == 2:
                cnt[1] += 1
            if c == 1:
                cnt[0] += 1
        c = 1
        
if c == 1:
    cnt[0] += 1
elif c == 2:
    cnt[1] += 1
elif c == 3:
    cnt[0] += 1
    cnt[1] += 1
elif c == 4:
    cnt[2] += 1
elif c > 4:
    cnt[2] += int(c / 4)
    c %= 4
    if c == 3:
        cnt[0] += 1
        cnt[1] += 1
    if c == 2:
        cnt[1] += 1
    if c == 1:
        cnt[0] += 1

ans = 1
#print(a, cnt, ans)
if a[2] > cnt[2]:
    ans = -1
cnt[2] -= a[2]
cnt[1] += cnt[2] * 2
#print(a, cnt, ans)
if a[1] > cnt[1]:
    ans = -1
cnt[1] -= a[1]
cnt[0] += cnt[1] * 2
#print(a, cnt, ans, 2)
if cnt[0] != a[0]:
    ans = -1
if ans == 1:
    print("Yes")
else:
    print("No")