#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <cstdlib>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional> 
#include <iomanip>
#include <unordered_map>
#include <memory.h>
#include <unordered_set>
#include <fstream>

using namespace std;

int dp[1001][1001];

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n, m;
	string s, t;

	cin >> n >> m;
	cin >> s;
	cin >> t;

	for (int i = 0; i <= 1000; i++)
	{
		for (int j = 0; j <= 1000; j++)
		{
			dp[i][j] = 1e9;
		}
	}

	for (int i = 1; i <= n; i++)
	{
		dp[i][0] = i;
	}
	for (int j = 1; j <= m; j++)
	{
		dp[0][j] = j;
	}
	dp[0][0] = 0;

	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= m; j++)
		{
			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);
				dp[i][j] = min(dp[i][j], dp[i - 1][j] + 1);
				dp[i][j] = min(dp[i][j], dp[i][j - 1] + 1);
			}
		}
	}

	cout << dp[n][m] << '\n';

	return 0;
}