using System;
using System.IO;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;

partial class Solver {

    public static int EditDistance<T>(string A, string B) {
        return EditDistance(A.ToCharArray(), B.ToCharArray());
    }
    public static int EditDistance<T>(T[] A, T[] B) where T : IEquatable<T> {
        int n = A.Length;
        int m = B.Length;
        var dp = new int[n + 1, m + 1];
        for (int i = 0; i <= n; i++) {
            dp[i, 0] = i;
        }
        for (int i = 0; i <= m; i++) {
            dp[0, i] = i;
        }
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (A[i].Equals(B[j])) {
                    dp[i + 1, j + 1] = Math.Min(dp[i, j + 1], dp[i + 1, j]) + 1;
                    dp[i + 1, j + 1] = Math.Min(dp[i + 1, j + 1], dp[i, j]);
                } else {
                    dp[i + 1, j + 1] = Math.Min(dp[i, j + 1], dp[i + 1, j]) + 1;
                    dp[i + 1, j + 1] = Math.Min(dp[i + 1, j + 1], dp[i, j] + 1);
                }

            }
        }
        return dp[n, m];
    }


    public void Run() {
        var n = ni();
        var m = ni();
        var s = ns();
        var t = ns();
        var d = EditDistance(s.ToArray(), t.ToArray());
        cout.WriteLine(d);
    }
}

// PREWRITEN CODE BEGINS FROM HERE
partial class Solver : Scanner {
    public static void Main(string[] args) {
        new Solver(Console.In, Console.Out).Run();
    }

    TextReader cin;
    TextWriter cout;

    public Solver(TextReader reader, TextWriter writer)
        : base(reader) {
        this.cin = reader;
        this.cout = writer;
    }
    public Solver(string input, TextWriter writer)
        : this(new StringReader(input), writer) {
    }

    public int ni() { return NextInt(); }
    public int[] ni(int n) { return NextIntArray(n); }
    public long nl() { return NextLong(); }
    public long[] nl(int n) { return NextLongArray(n); }
    public double nd() { return NextDouble(); }
    public string ns() { return Next(); }
    public string[] ns(int n) { return NextArray(n); }
}

public class Scanner {
    private TextReader Reader;
    private Queue<String> TokenQueue = new Queue<string>();
    private CultureInfo ci = CultureInfo.InvariantCulture;

    public Scanner()
        : this(Console.In) {
    }

    public Scanner(TextReader reader) {
        this.Reader = reader;
    }

    public int NextInt() { return Int32.Parse(Next(), ci); }
    public long NextLong() { return Int64.Parse(Next(), ci); }
    public double NextDouble() { return double.Parse(Next(), ci); }
    public string[] NextArray(int size) {
        var array = new string[size];
        for (int i = 0; i < size; i++) array[i] = Next();
        return array;
    }
    public int[] NextIntArray(int size) {
        var array = new int[size];
        for (int i = 0; i < size; i++) array[i] = NextInt();
        return array;
    }

    public long[] NextLongArray(int size) {
        var array = new long[size];
        for (int i = 0; i < size; i++) array[i] = NextLong();
        return array;
    }

    public String Next() {
        if (TokenQueue.Count == 0) {
            if (!StockTokens()) throw new InvalidOperationException();
        }
        return TokenQueue.Dequeue();
    }

    public bool HasNext() {
        if (TokenQueue.Count > 0)
            return true;
        return StockTokens();
    }

    private bool StockTokens() {
        while (true) {
            var line = Reader.ReadLine();
            if (line == null) return false;
            var tokens = line.Trim().Split(" ".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
            if (tokens.Length == 0) continue;
            foreach (var token in tokens)
                TokenQueue.Enqueue(token);
            return true;
        }
    }
}