package no225;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		char[] s = sc.next().toCharArray();
		char[] t = sc.next().toCharArray();
		System.out.println(levenshteinDistance(s, t));
	}

	public static int levenshteinDistance(char[] s,char[] t) {
		int n = s.length;
		int m = t.length;
		int[][] 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=1;i<=n;i++) {
			for(int j=1;j<=m;j++) {
				dp[i][j] = Math.min(dp[i-1][j] + 1, Math.min(dp[i][j-1] + 1, dp[i-1][j-1] + (s[i-1] == t[j-1] ? 0 : 1)));
			}
		}
//		System.out.println(Arrays.deepToString(dp));
		return dp[n][m];
	}
}