using System;

namespace No225_1{
    public class Program{
        public static void Main(string[] args){
            var input = Console.ReadLine().Split(' ');
            var n = int.Parse(input[0]);
            var m = int.Parse(input[1]);
            var s = " " + Console.ReadLine();
            var t = " " + Console.ReadLine();
            var dp = new int[n + 1, m + 1];

            for(var i = 0; i <= n; i++) dp[i, 0] = i;
            for(var j = 0; j <= m; j++) dp[0, j] = j;

            for(var i = 1; i <= n; i++){
                for(var j = 1; j <= m; j++){
                    var min = Math.Min(dp[i - 1, j] + 1, dp[i, j - 1] + 1);
                    dp[i, j] = s[i] == t[j] ? Math.Min(min, dp[i - 1, j - 1]) : Math.Min(min, dp[i - 1, j - 1] + 1);
                }
            }

            Console.WriteLine(dp[n, m]);
        }
    }
}