package main

import (
	"fmt"
	"strings"
)

func main() {
	var n, m int
	var S, T string
	fmt.Scan(&n, &m, &S, &T)
	s:= strings.Split(S,"")
	t:= strings.Split(T,"")
	fmt.Println(lesvenshteinDistance(s, t))
}

func lesvenshteinDistance(str1 []string, str2 []string)int{
	d := makeDoubleSliceInt(len(str1)+1, len(str2)+1)
	cost:=0
	for i1 :=0; i1<len(str1);i1++{
		d[i1][0]=i1
	}
	for i2:=0; i2<len(str2);i2++{
		d[0][i2] = i2
	}
	for i:=1;i<len(str1);i++{
		for j:=1;j<len(str2);j++{
			if str1[i]==str2[j]{
				cost=0
			}else{
				cost=1
			}
			d[i][j]=min(d[i-1][j]+1, min(d[i][j-1]+1, d[i-1][j-1]+cost))
		}
	}
	//fmt.Println(d)
	return d[len(str1)-1][len(str2)-1]
}

func makeDoubleSliceInt(y, x int) [][]int {
	ss := make([][]int, y)
	for i := range ss {
		ss[i] = make([]int, x)
	}
	return ss
}

func min(a, b int) int {
	if a < b {
		a, b = b, a
	}
	return b
}