#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int n, m; cin >> n >> m;
	string S, T; cin >> S >> T;
	vector<vector<int> > dp(n + 1, vector<int>(m + 1));
	for (int i = 0; i <= n; i++)
		dp[i][0] = i;
	for (int j = 0; j <= m; j++)
		dp[0][j] = j;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++) {
			dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + 1;
			if (S[i - 1] == T[j - 1])
				dp[i][j] = min(dp[i][j], dp[i - 1][j - 1]);
			else
				dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + 1);
		}
	cout << dp[n][m] << endl;
}