Problem:
Score : 400 points

Problem Statement

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.

Note

A palindrome is a string that reads the same forward and backward.
For example, a, aa, abba and abcba are all palindromes, while ab, abab and abcda are not.

Constraints

1 ≤ H, W ≤ 100

a_{ij} is a lowercase English letter.

Input

Input is given from Standard Input in the following format:

H W
a_{11}a_{12}...a_{1W}
:
a_{H1}a_{H2}...a_{HW}

Output

If Snuke can create a matrix satisfying the condition, print Yes; otherwise, print No.

Sample Input 1

3 4
aabb
aabb
aacc

Sample Output 1

Yes

For example, the following matrix satisfies the condition.

abba
acca
abba

Sample Input 2

2 2
aa
bb

Sample Output 2

No

It is not possible to create a matrix satisfying the condition, no matter how we rearrange the elements in A.

Sample Input 3

5 1
t
w
e
e
t

Sample Output 3

Yes

For example, the following matrix satisfies the condition.

t
e
w
e
t

Sample Input 4

2 5
abxba
abyba

Sample Output 4

No

Sample Input 5

1 1
z

Sample Output 5

Yes

Solution in Python (3.8.2) (judge verdict: Wrong Answer)

from collections import Counter
 
h, w = map(int, input().split())
a = Counter(''.join(input() for _ in range(h)))
 
center = h * w % 2 
side = (h//2) * (w%2) + (w//2) * (h%2)
corner = (h//2) * (w//2)

for _ in range(center):
    for i in a:
        if a[i] % 2 == 1:
            a[i] -= 1
            break
for _ in range(side):
    for j in a:
        if a[j] % 4 == 2:
            a[j] -= 2
            break
for _ in range(corner):
    for k in a:
        if a[k]!=0 and a[k] % 4 == 0:
            a[k] -= 4
            break
            
#print('Yes' if sum(a[i] for i in a) == 0 else 'No')
print("Yes" if all(list(map(lambda x:x==0,a.values()))) else "No")