#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<vector>
#include<queue>
#define rep(index,num) for(int index=0;index<num;index++)
#define scan(argument) cin>>argument
#define prin(argument) cout<<argument<<endl
#define kaigyo cout<<endl
#define eps 1e-15
typedef long long ll;
using namespace std;
typedef pair<int,int> pint;
const int INF = 1<<29;
int main(){
	string S,T;
	int n,m;
	scan(n);scan(m);
	scan(S);scan(T);
	int dp[1001][1001];
	rep(i,S.size()+1){
		dp[i][0]=i;
	}
	rep(j,T.size()+1){
		dp[0][j]=j;
	}
	rep(i,S.size()){
		rep(j,T.size()){
			if(S[i]==T[j]) dp[i+1][j+1]=min(dp[i][j],min(dp[i][j+1]+1,dp[i+1][j]+1));
			else dp[i+1][j+1]=min(dp[i][j]+1,min(dp[i][j+1]+1,dp[i+1][j]+1));
		}
	}
	prin(dp[S.size()][T.size()]);
	return 0;
}