#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ull mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int n,m;
string s,t;
vvi dp;

int main(){
	cin>>n>>m>>s>>t;
	dp=vvi(n+1,vi(m+1));
	for(int i=0;i<=n;i++) for(int j=0;j<=m;j++) if(i||j){
		if(i&&!j) dp[i][j]=i;
		else if(!i&&j) dp[i][j]=j;
		else{
			if(s[i-1]==t[j-1]) dp[i][j]=dp[i-1][j-1];
			else dp[i][j]=min({dp[i-1][j],dp[i][j-1],dp[i-1][j-1]})+1;
		}
	}
	cout<<dp[n][m]<<endl;
}