#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
#include<bitset>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())
#define indexOf(v,x) (find(all(v),x)-v.begin())


int dp[1001][1001];

int main(){
	int n,m;
	string s,t;
	cin>>n>>m;
	cin>>s>>t;
	fill(dp[0],dp[1001],INF);
	dp[0][0]=0;
	rep(i,n+1)rep(j,m+1){
		if(i<n&&j<m)dp[i+1][j+1]=min(dp[i+1][j+1],dp[i][j]+(s[i]!=t[j]));
		if(i<n)dp[i+1][j]=min(dp[i+1][j],dp[i][j]+1);
		if(j<m)dp[i][j+1]=min(dp[i][j+1],dp[i][j]+1);
	}
	cout<<dp[n][m]<<endl;
	return 0;
}