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 Ruby (2.3.3) (judge verdict: Accepted)

h, w = gets.split.map(&:to_i)

(c = {}).default = 0
h.times {gets.chomp.each_char {|e| c[e] += 1}}

(x = {}).default = 0
c.each_value {|e| x[e % 4] += 1}

case 2 * (h % 2) + w % 2
when 3
    puts x[1] + x[3] == 1 && (x[2] + x[3]) * 2 <= h + w - 2 && (h + w - 2 - (x[2] + x[3]) * 2) % 4 == 0 ? "Yes" : "No"
when 2
    puts x[1] + x[3] == 0 && x[2] * 2 <= w && (w - x[2] * 2) % 4 == 0 ? "Yes" : "No"
when 1
    puts x[1] + x[3] == 0 && x[2] * 2 <= h && (h - x[2] * 2) % 4 == 0 ? "Yes" : "No"
when 0
    puts x[1] + x[2] + x[3] == 0 ? "Yes" : "No"
end