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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using static System.Console;
using Pair = System.Collections.Generic.KeyValuePair<int, int>;
//using System.Numerics;
//using static System.Math;

class Program
{
    static void Main()
    {
        //SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
        new Program().solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 };
    readonly int mod = 1000000007;
    readonly string alfa = "abcdefghijklmnopqrstuvwxyz";
    readonly string ALFA = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    //int N;
    int H, W;
    void solve()
    {
        H = cin.nextint;
        W = cin.nextint;
        var A = new int[26];
        for (int i = 0; i < H; i++)
        {
            var S = cin.next;
            for (int j = 0; j < W; j++)
            {
                int k = S[j] - 'a';
                A[k]++;
            }
        }

        int min = A.Min();

        bool flag = true;


        int guu = 0;
        int ki = 0;
        int one = 0;
        for (int i = 0; i < 26; i++)
        {
            if (A[i] == 1)
            {
                one++;
            }
            if (A[i] % 2 == 1)
            {
                ki++;
            }
            else if (A[i] > 0)
            {
                guu++;
            }
        }

        if (H % 2 == 0 && W % 2 == 0)
        {
            for (int i = 0; i < 26; i++)
            {
                if (A[i] % 4 != 0)
                {
                    flag = false;
                }
            }
        }
        else if (H % 2 == 0 || W % 2 == 0)
        {
            int d;
            if (H % 2 == 0)
            {
                d = H / 2;
            }
            else
            {
                d = W / 2;
            }
            for (int i = 0; i < 26; i++)
            {
                if (A[i] % 2 != 0)
                {
                    flag = false;
                }
                A[i] /= 2;
            }
            var E = new int[2];
            for (int i = 0; i < 26; i++)
            {
                if (A[i] == 0) continue;
                E[A[i] % 2]++;
            }
            if (E[1] > d)
            {
                flag = false;
            }
        }


        else
        {
            var E = new int[4];
            for (int i = 0; i < 26; i++)
            {
                if (A[i] == 0) continue;
                E[A[i] % 4]++;
            }
            if (E[1] + E[3] > H / 2 + W / 2 + 1)
            {
                flag = false;
            }
        }

        WriteLine(flag ? "Yes" : "No");
    }

}

class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan { get { return ReadLine().Split(); } }
    public int[] scanint { get { return Array.ConvertAll(scan, int.Parse); } }
    public long[] scanlong { get { return Array.ConvertAll(scan, long.Parse); } }
    public double[] scandouble { get { return Array.ConvertAll(scan, double.Parse); } }
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint { get { return int.Parse(next); } }
    public long nextlong { get { return long.Parse(next); } }
    public double nextdouble { get { return double.Parse(next); } }
}

//else if (W % 2 == 0)
//{
//    for (int i = 0; i < 26; i++)
//    {
//        if (A[i] % 2 == 1)
//        {
//            flag = false;
//        }
//        A[i] /= 2;
//    }
//}

//if (H == 1 || W == 1)
//{
//    if (H == 1)
//    {
//        if (W % 2 == 1)
//        {
//            if (ki == 1)
//            {
//                flag = true;
//            }
//            else
//            {
//                flag = false;
//            }
//        }
//    }
//    else
//    {
//        if (H % 2 == 1)
//        {
//            if (ki == 1)
//            {
//                flag = true;
//            }
//            else
//            {
//                flag = false;
//            }
//        }
//    }
//}