#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1 << 28;
constexpr long long mod = 1000000007LL;
//constexpr long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;


int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/

	int n, m; scanf("%d %d", &n, &m);
	string s, t; cin >> s >> t;
	vector<vector<int>> dp(s.size() + 1, vector<int>(t.size() + 1, inf));
	for (int i = 0; i <= t.size(); i++) {
		dp[0][i] = i;
	}
	for (int i = 0; i <= s.size(); i++) {
		dp[i][0] = i;
	}
	for (int i = 0; i < s.size(); i++) {
		for (int j = 0; j < t.size(); j++) {
			if (s[i] == t[j]) chmin(dp[i + 1][j + 1], dp[i][j]);
			else chmin(dp[i + 1][j + 1], dp[i][j] + 1);
			chmin(dp[i + 1][j + 1], dp[i + 1][j] + 1);
			chmin(dp[i + 1][j + 1], dp[i][j + 1] + 1);
		}
	}
	cout << dp[n][m] << endl;
    return 0;
}