import java.util.*;
import java.math.*;

public class Main {
    static int[][] dp;
    static char[] aArr;
    static char[] bArr;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        dp = new int[n][m];
        aArr = sc.next().toCharArray();
        bArr = sc.next().toCharArray();
        System.out.println(getCount(0, 0));
    }
    
    static int getCount(int aIdx, int bIdx) {
        if (aIdx == aArr.length) {
            return bArr.length - bIdx;
        }
        if (bIdx == bArr.length) {
            return aArr.length - aIdx;
        }
        if (dp[aIdx][bIdx] != 0) {
            return dp[aIdx][bIdx];
        }
        int min;
        if (aArr[aIdx] == bArr[bIdx]) {
            min = getCount(aIdx + 1, bIdx + 1);
        } else {
            min = getCount(aIdx + 1, bIdx + 1) + 1;
            min = Math.min(min, getCount(aIdx + 1, bIdx) + 1);
            min = Math.min(min, getCount(aIdx, bIdx + 1) + 1);
        }
        dp[aIdx][bIdx] = min;
        return min;
    }
}