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 PyPy3 (2.4.0) (judge verdict: Wrong Answer)

# def makelist(n, m):
#     return [[0 for i in range(m)] for j in range(n)]

yes = "Yes"
no = "No"

H, W = map(int, input().split())
alph = [0]*26

for i in range(H):
    for c in input():
        alph[ord(c) - 97] += 1

four = 0
two = 0
one = 0
ans = no
for e in alph:
    four += e // 4
    e %= 4
    two += e // 2
    one += e % 2
        
if (H, W) == (1, 1):
    ans = yes
else:
    if H % 2 == 0 and W % 2 == 0:
        if one > 0 or two > 0:
            ans = no
        else:
            ans = yes
    elif H % 2 == 0 and W % 2 == 1:
        if one == 1 and two == H // 2:
            ans = yes
    elif H % 2 == 1 and W % 2 == 0:
        if one == 1 and two == W // 2:
            ans = yes
    elif H % 2 == 1 and W % 2 == 1:
        if one == 1 and two == H // 2 + W // 2:
            ans = yes

print(ans)