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.
//package cf683;

import java.io.*;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Random;
import java.util.StringTokenizer;
import java.util.function.Function;
import java.util.stream.Collectors;

// What's the smallest input?
// Check * for int/long overflow.
// Check / for accidental rounding.
// Are you using doubles? Can you avoid it?
// Never compare after taking mod.
// Mod the final result.
// Initialize globals in solve() unless they are independent of the problem input.
// Check for local/global name conflicts (n?).
// Check initial values for max/min (not Integer.MIN_VALUE for long).
public class D {
    static Random rand;
    static boolean MULTIPLE_CASES = false;
    static boolean CONSTRUCTIVE = false;
    static long MOD = (long) 1e9 + 7;
    static long BIG = (long) 2e9 + 10;

    public static void solve(Reader in, PrintWriter out) {
        int n = in.ni(), m = in.ni();
        char[] a = in.next().toCharArray();
        char[] b = in.next().toCharArray();

        int[][] dp = new int[n + 1][m + 1];

        int best = 0;
        for (int i = 0; i <= n; i++) {
            for (int j = 0; j <= m; j++) {
                if (i == 0 || j == 0) {
                    dp[i][j] = -(i + j);
                } else if (a[i - 1] == b[j - 1]) {
                    dp[i][j] = dp[i - 1][j - 1] + 2;
                } else {
                    dp[i][j] = Math.max(dp[i - 1][j] - 1, dp[i][j - 1] - 1);
                }
                dp[i][j] = Math.max(0, dp[i][j]);
                best = Math.max(best, dp[i][j]);
            }
        }
//        System.err.println(Arrays.deepToString(L));
        out.println(best);
    }

    public static void main(String[] args) throws IOException {
        Reader in = null;
        PrintWriter out = null;
        for (String arg : args) {
            if (arg.startsWith("input")) {
                in = new Reader(arg);
            } else if (arg.startsWith("output")) {
                out = new PrintWriter(new FileWriter(arg));
            }
        }
        if (in == null) in = new Reader();
        if (out == null) out = new PrintWriter(new OutputStreamWriter(System.out));

        if (MULTIPLE_CASES) {
            int tests = in.ni();
            for (int t = 0; t < tests; t++) {
                solve(in, out);
            }
        } else {
            solve(in, out);
        }

        out.flush();
    }

    static class Tester {
        public static void main(String[] args) throws IOException {
            Validator validator = new Validator();

            File currentDir = new File(".");
            long before;
            long after;
            for (File inputFile : Arrays.stream(currentDir.listFiles())
                    .sorted(Comparator.comparing(File::getName))
                    .collect(Collectors.toList())) {
                if (!inputFile.getName().startsWith("input")
                        || inputFile.getName().contains("sight")
                        || inputFile.getName().contains("big")) continue;
                System.out.println("Test file: " + inputFile.getName());

                before = System.nanoTime();
                String outputFileName = "output" + inputFile.getName().substring(5);
                D.main(new String[]{inputFile.getName(), outputFileName});
                after = System.nanoTime();

                File outputFile = new File(outputFileName);
                if (!outputFile.exists()) {
                    throw new IllegalStateException("Missing output file " + outputFile);
                }

                // TODO if verifier is implemented, remove this
                if (CONSTRUCTIVE) {
                    System.out.println("INPUT:");
                    printFile(inputFile);
                    System.out.printf("\nOUTPUT: (%d milliseconds)\n", (after - before) / 1000000L);
                    printFile(outputFile);
                    continue;
                }

                if (validator.validate(inputFile, outputFile)) {
                    System.out.printf("OK (%d milliseconds)\n", (after - before) / 1000000L);
                } else {
                    System.out.println("FAILED");
                    System.out.println("\nInput: ");
                    printFile(inputFile);
                    System.out.println("\nIncorrect Output: ");
                    printFile(outputFile);
                    return;
                }
            }
            System.out.println("\n-----------------\n");

            File sightTestInput = new File("input-sight");
            if (sightTestInput.exists()) {
                System.out.println("Running sight test... Input:");
                printFile(sightTestInput);
                before = System.nanoTime();
                System.out.println("\nOutput: ");
                D.main(new String[]{"input-sight"});
                after = System.nanoTime();
                System.out.printf("(%d milliseconds)\n", (after - before) / 1000000L);
                System.out.println("\n-----------------\n");
            }

            File bigTestInput = new File("input-big");
            if (bigTestInput.exists()) {
                System.out.println("Running big test...");
                before = System.nanoTime();
                D.main(new String[]{"input-big"});
                after = System.nanoTime();
                System.out.printf("(%d milliseconds)\n", (after - before) / 1000000L);
            }
        }

        static void printFile(File file) throws FileNotFoundException {
            BufferedReader reader = new BufferedReader(new FileReader(file));
            reader.lines().forEach(System.out::println);
        }
    }

    static class Validator {
        boolean validate(File inputFile, File outputFile) throws IOException {
            File expectedOutputFile = new File("expected-output" + inputFile.getName().substring(5));
            if (CONSTRUCTIVE || !expectedOutputFile.exists()) {
                return validateManual(inputFile, outputFile);
            }
            return areSame(outputFile, expectedOutputFile);
        }

        private boolean validateManual(File inputFile, File outputFile) throws IOException {
            if (CONSTRUCTIVE) {
                // Validate output against input
                Reader inputReader = new Reader(inputFile.getName());
                Reader outputReader = new Reader(outputFile.getName());

                // TODO implement manual validation

                throw new IllegalStateException("Missing expected output file");
            } else {
                File naiveOutput = new File("naive-" + outputFile.getName());
                Naive.main(new String[]{inputFile.getName(), naiveOutput.getName()});

                return areSame(outputFile, naiveOutput);
            }
        }

        private boolean areSame(File file1, File file2) throws IOException {
            BufferedReader reader1 = new BufferedReader(new FileReader(file1));
            BufferedReader reader2 = new BufferedReader(new FileReader(file2));

            String line1;
            while ((line1 = reader1.readLine()) != null) {
                String line2 = reader2.readLine();
                if (line2 == null) line2 = ""; // ok if one has an extra newline
                if (!line1.trim().equals(line2.trim())) {
                    return false;
                }
            }
            String line2;
            while ((line2 = reader2.readLine()) != null) {
                if (!line2.trim().isEmpty()) {
                    return false;
                }
            }
            return true;
        }

    }

    static class Naive {
        public static void solveNaive(Reader in, PrintWriter out) {
            throw new IllegalStateException("missing expected output file");
        }

        public static void main(String[] args) throws IOException {
            Reader in = null;
            PrintWriter out = null;
            for (String arg : args) {
                if (arg.startsWith("input")) {
                    in = new Reader(arg);
                } else if (arg.startsWith("naive-output")) {
                    out = new PrintWriter(new FileWriter(arg));
                }
            }
            if (in == null) in = new Reader();
            if (out == null) out = new PrintWriter(new OutputStreamWriter(System.out));

            int tests = in.ni();
            for (int t = 0; t < tests; t++) {
                solveNaive(in, out);
            }

            out.flush();
            out.close();
        }
    }

    static boolean isPowerOfTwo(int x) {
        return x > 0 & (x & (x - 1)) == 0;
    }

    static int gcd(int a, int b) {
        return b == 0 ? a : gcd(b, a % b);
    }

    static void ruffleSort(int[] a) {
        int n = a.length;
        for (int i = 0; i < n; i++) {
            int oi = rand.nextInt(n), temp = a[oi];
            a[oi] = a[i];
            a[i] = temp;
        }
        Arrays.sort(a);
    }

    static void ruffleSort(long[] a) {
        int n = a.length;
        for (int i = 0; i < n; i++) {
            int oi = rand.nextInt(n);
            long temp = a[oi];
            a[oi] = a[i];
            a[i] = temp;
        }
        Arrays.sort(a);
    }

    ///////////////////////////////////
    //////////   FAST PAIR   //////////
    ///////////////////////////////////

    // Works on -1e9 <= x, y <= 1e9
    static long pair(int x, int y) {
        x = (int) BIG / 2 - x;
        y = (int) BIG / 2 - y;
        return x * BIG + y;
    }

    static int x(long pair) {
        return (int) BIG / 2 - (int) (pair / BIG);
    }

    static int y(long pair) {
        return (int) BIG / 2 - (int) (pair % BIG);
    }

    static String str(long pair) {
        return String.format("(%d, %d)", x(pair), y(pair));
    }

    ///////////////////////////////////
    ////////// BINARY SEARCH //////////
    ///////////////////////////////////

    // return highest in range that still returns true
    // T T T F F F F
    // invariant:
    // -    indicator(min) = true
    // -    indicator(max+1) = false
    static int binarySearchHighest(int min, int max, Function<Integer, Boolean> indicator) {
        int a = min;
        int b = max;
        while (a != b) {
            int mid = (a % 2 != b % 2) ? 1 + (a + b) / 2 : (a + b) / 2;
            if (indicator.apply(mid)) {
                a = mid;
            } else {
                b = mid - 1;
            }
        }
        return a;
    }

    // return lowest in range that still returns true
    // F F F F T T T
    // invariant:
    // -    indicator(min-1) = false
    // -    indicator(max) = true
    static int binarySearchLowest(int min, int max, Function<Integer, Boolean> indicator) {
        int a = min;
        int b = max;
        while (a != b) {
            int mid = (a + b) / 2;
            if (indicator.apply(mid)) {
                b = mid;
            } else {
                a = mid + 1;
            }
        }
        return a;
    }

    static void insist(boolean bool) {
        if (!bool) throw new IllegalStateException();
    }

    static class Reader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public Reader() {
            reader = new BufferedReader(new InputStreamReader(System.in), 32768);
            tokenizer = null;
        }

        public Reader(String fileName) throws FileNotFoundException {
            reader = new BufferedReader(new FileReader(fileName));
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int ni() {
            return Integer.parseInt(next());
        }

        public long nl() {
            return Long.parseLong(next());
        }

        public int[] nis(int n) {
            int[] out = new int[n];
            for (int i = 0; i < n; i++) {
                out[i] = ni();
            }
            return out;
        }

        public long[] nls(int n) {
            long[] out = new long[n];
            for (int i = 0; i < n; i++) {
                out[i] = nl();
            }
            return out;
        }
    }
}
