You are given two strings A and B representing essays of two students who are suspected cheaters. For any two strings C, D we define their similarity score S(C,D) as 4⋅ LCS(C,D) - |C| - |D|, where LCS(C,D) denotes the length of the Longest Common Subsequence of strings C and D. 

You believe that only some part of the essays could have been copied, therefore you're interested in their substrings.

Calculate the maximal similarity score over all pairs of substrings. More formally, output maximal S(C, D) over all pairs (C, D), where C is some substring of A, and D is some substring of B. 

If X is a string, |X| denotes its length.

A string a is a substring of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.

A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters. 

Pay attention to the difference between the substring and subsequence, as they both appear in the problem statement. 

You may wish to read the [Wikipedia page about the Longest Common Subsequence problem](https://en.wikipedia.org/wiki/Longest_common_subsequence_problem).

Input

The first line contains two positive integers n and m (1 ≤ n, m ≤ 5000) — lengths of the two strings A and B. 

The second line contains a string consisting of n lowercase Latin letters — string A.

The third line contains a string consisting of m lowercase Latin letters — string B. 

Output

Output maximal S(C, D) over all pairs (C, D), where C is some substring of A, and D is some substring of B. 

Examples

Input


4 5
abba
babab


Output


5

Input


8 10
bbbbabab
bbbabaaaaa


Output


12

Input


7 7
uiibwws
qhtkxcn


Output


0

Note

For the first case:

abb from the first string and abab from the second string have LCS equal to abb.

The result is S(abb, abab) = (4 ⋅ |abb|) - |abb| - |abab| = 4 ⋅ 3 - 3 - 4 = 5.
import java.util.*;
import java.io.*;
import java.math.*;

/**
 * Author    : joney_000[developer.jaswant@gmail.com]
 * Algorithm : Extended Euclid Algo: find 3 things X, Y, GCD(A, B) Such that X * A + Y * B = GCD(A, B)
 *             Time : O(MAX(A, B)) Space : O(MAX(A, B))
 * Platform  : Codeforces
 * Ref       : https://www.hackerearth.com/practice/math/number-theory/basic-number-theory-1/tutorial/
 */

 public class A{ 
  
  private InputStream inputStream ;
  private OutputStream outputStream ;
  private FastReader in ;
  private PrintWriter out ;
  
  private final int  INF  = Integer.MAX_VALUE;
  private final long INF_L  = Long.MAX_VALUE / 10;

  public A(){}
  public A(boolean stdIO)throws FileNotFoundException{
    if(stdIO){
      inputStream = System.in;
      outputStream = System.out;
    }else{
      inputStream = new FileInputStream("input.txt");
      outputStream = new FileOutputStream("output.txt");
    }
    in = new FastReader(inputStream);
    out = new PrintWriter(outputStream);
  }
  int dp[][];

  void run()throws Exception{
    int n = i();
    int m = i();
    dp = new int[n + 1][m + 1];
    // for(int i = 1; i <= n; i++){
    //   for(int j = 1; j <= m; j++){
    //     dp[
    //   }
    // }
    String a = s();
    String b = s();
    int ans = 0;
    for(int i = 1; i <= n; i++){
      for(int j = 1; j <= m; j++){
        if(a.charAt(i-1) == b.charAt(j-1)){
          dp[i][j] = 2;// assuming subarray start from here
          dp[i][j] = Math.max(dp[i][j], 2 + dp[i - 1][j - 1]);
        }else{
          dp[i][j] = -2;// assuming subarray start from here
          dp[i][j] = Math.max(dp[i][j], -2 + dp[i - 1][j  -1]);
        }
        dp[i][j] = Math.max(dp[i][j], Math.max(-1 + dp[i][j - 1], -1 + dp[i - 1][j]));
        ans = Math.max(dp[i][j], ans);
      }
    }
    out.write(""+ans+"\n");
  }

  void clear(){
    throw new UnsupportedOperationException("implementation of clear vary based on use case");
  }

  long gcd(long a, long b){
    if(b == 0)return a;
    return gcd(b, a % b);
  }

  long lcm(long a, long b){
    if(a == 0 || b == 0)return 0;
    return (a * b)/gcd(a, b);
  }

  long mulMod(long a, long b, long mod){
    if(a == 0 || b == 0)return 0;
    if(b == 1)return a;
    long ans = mulMod(a, b/2, mod);
    ans = (ans * 2) % mod;
    if(b % 2 == 1)ans = (a + ans)% mod;
    return ans;
  }

  long pow(long a, long b, long mod){
    if(b == 0)return 1;
    if(b == 1)return a;
    long ans = pow(a, b/2, mod);
    ans = mulMod(ans, ans, mod);
    if(ans >= mod)ans %= mod;

    if(b % 2 == 1)ans = mulMod(a, ans, mod);
    if(ans >= mod)ans %= mod;

    return ans;
  }

  // 20*20   nCr Pascal Table
  long[][] ncrTable(){
    long ncr[][] = new long[21][21];

    for(int i = 0; i <= 20; i++){
      ncr[i][0] = ncr[i][i] = 1L;
    }

    for(int j = 0; j <= 20; j++){
      for(int i = j + 1; i <= 20; i++){
        ncr[i][j] = ncr[i-1][j] + ncr[i-1][j-1];
      }
    }

    return ncr;
  }

  int i()throws Exception{
    return in.nextInt();
  }

  long l()throws Exception{
    return in.nextLong();
  }

  double d()throws Exception{
    return in.nextDouble();
  }

  char c()throws Exception{
    return in.nextCharacter();
  }

  String s()throws Exception{
    return in.nextLine();
  }

  BigInteger bi()throws Exception{
    return in.nextBigInteger();
  }
  
  private void closeResources(){
    out.flush();
    out.close();
    return;
  }

//  IMP: roundoff upto 2 digits 
//  double roundOff = Math.round(a * 100.0) / 100.0;
//                    or
//  System.out.printf("%.2f", val);

//  print upto 2 digits after decimal
//  val = ((long)(val * 100.0))/100.0;    

  public static void main(String[] args) throws java.lang.Exception{
  
    A driver = new A(true);
    driver.run();
    driver.closeResources();
  }
}

class FastReader{

  private boolean finished = false;

  private InputStream stream;
  private byte[] buf = new byte[4 * 1024];
  private int curChar;
  private int numChars;
  private SpaceCharFilter filter;

  public FastReader(InputStream stream){
    this.stream = stream;
  }

  public int read(){
    if (numChars == -1){
      throw new InputMismatchException ();
    }
    if (curChar >= numChars){
      curChar = 0;
      try{
        numChars = stream.read (buf);
      } catch (IOException e){
        throw new InputMismatchException ();
      }
      if (numChars <= 0){
        return -1;
      }
    }
    return buf[curChar++];
  }

  public int peek(){
    if (numChars == -1){
      return -1;
    }
    if (curChar >= numChars){
      curChar = 0;
      try{
        numChars = stream.read (buf);
      } catch (IOException e){
        return -1;
      }
      if (numChars <= 0){
        return -1;
      }
    }
    return buf[curChar];
  }

  public int nextInt(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    int sgn = 1;
    if (c == '-'){
      sgn = -1;
      c = read ();
    }
    int res = 0;
    do{
      if(c==','){
        c = read();
      }
      if (c < '0' || c > '9'){
        throw new InputMismatchException ();
      }
      res *= 10;
      res += c - '0';
      c = read ();
    } while (!isSpaceChar (c));
    return res * sgn;
  }

  public long nextLong(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    int sgn = 1;
    if (c == '-'){
      sgn = -1;
      c = read ();
    }
    long res = 0;
    do{
      if (c < '0' || c > '9'){
        throw new InputMismatchException ();
      }
      res *= 10;
      res += c - '0';
      c = read ();
    } while (!isSpaceChar (c));
    return res * sgn;
  }

  public String nextString(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    StringBuilder res = new StringBuilder ();
    do{
      res.appendCodePoint (c);
      c = read ();
    } while (!isSpaceChar (c));
    return res.toString ();
  }

  public boolean isSpaceChar(int c){
    if (filter != null){
      return filter.isSpaceChar (c);
    }
    return isWhitespace (c);
  }

  public static boolean isWhitespace(int c){
    return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
  }

  private String readLine0(){
    StringBuilder buf = new StringBuilder ();
    int c = read ();
    while (c != '\n' && c != -1){
      if (c != '\r'){
        buf.appendCodePoint (c);
      }
      c = read ();
    }
    return buf.toString ();
  }

  public String nextLine(){
    String s = readLine0 ();
    while (s.trim ().length () == 0)
      s = readLine0 ();
    return s;
  }

  public String nextLine(boolean ignoreEmptyLines){
    if (ignoreEmptyLines){
      return nextLine ();
    }else{
      return readLine0 ();
    }
  }

  public BigInteger nextBigInteger(){
    try{
      return new BigInteger (nextString ());
    } catch (NumberFormatException e){
      throw new InputMismatchException ();
    }
  }

  public char nextCharacter(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    return (char) c;
  }

  public double nextDouble(){
    int c = read ();
    while (isSpaceChar (c))
      c = read ();
    int sgn = 1;
    if (c == '-'){
      sgn = -1;
      c = read ();
    }
    double res = 0;
    while (!isSpaceChar (c) && c != '.'){
      if (c == 'e' || c == 'E'){
        return res * Math.pow (10, nextInt ());
      }
      if (c < '0' || c > '9'){
        throw new InputMismatchException ();
      }
      res *= 10;
      res += c - '0';
      c = read ();
    }
    if (c == '.'){
      c = read ();
      double m = 1;
      while (!isSpaceChar (c)){
        if (c == 'e' || c == 'E'){
          return res * Math.pow (10, nextInt ());
        }
        if (c < '0' || c > '9'){
          throw new InputMismatchException ();
        }
        m /= 10;
        res += (c - '0') * m;
        c = read ();
      }
    }
    return res * sgn;
  }

  public boolean isExhausted(){
    int value;
    while (isSpaceChar (value = peek ()) && value != -1)
      read ();
    return value == -1;
  }

  public String next(){
    return nextString ();
  }

  public SpaceCharFilter getFilter(){
    return filter;
  }

  public void setFilter(SpaceCharFilter filter){
    this.filter = filter;
  }

  public interface SpaceCharFilter{
    public boolean isSpaceChar(int ch);
  }
}

class Pair implements Comparable<Pair>{
  public int a;
  public int b;
   
  public Pair(){
    this.a = 0;
    this.b = 0;
  }

  public Pair(int a,int b){
    this.a = a;
    this.b = b;
  }

  public int compareTo(Pair p){
    if(this.a == p.a){
     return this.b - p.b;  
   }
   return this.a - p.a; 
  }

  @Override
  public String toString(){
    return "a = " + this.a + " b = " + this.b;
  }
} 