#include"bits/stdc++.h"

//#include<bits/stdc++.h>
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
typedef pair<int, int> PI;
typedef pair<int, PI> V;
typedef vector<int> VE;
const ll mod = 100000000000;

int n, m;
string s, t;
int d[1002][1002];

int main() {
	cin >> n >> m;
	cin >> s;
	cin >> t;
	REP(i, n + 1)REP(j, m + 1)d[i][j] = mod;
	REP(i, n+1)d[i][0] = i;
	REP(i, m+1)d[0][i] = i;
	REP(i, n+1)REP(j, m+1) {
		int cost = s[i] == t[j] ? 0 : 1;
		d[i][j] = min(d[i - 1][j] + 1, min(d[i][j - 1] + 1, d[i - 1][i - 1] + cost));
	}
	print(d[n][m]);
	return 0;
}