#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <numeric>
#include <bitset>
#include <complex>
#define rep(x, to) for (int x = 0; x < (to); x++)
#define REP(x, a, to) for (int x = (a); x < (to); x++)
#define foreach(itr, x) for (typeof((x).begin()) itr = (x).begin(); itr != (x).end(); itr++)
#define EPS (1e-14)

using namespace std;

typedef long long ll;
typedef pair<int, int> PII;
typedef pair<long, long> PLL;

int n, m;
string s, t;

ll memo[1005][1005];

ll dfs(int i, int j) {
	ll res = 0;
	if (i >= n) return m - j;
	if (j >= m) return n - i;
	if (memo[i][j] != -1) return memo[i][j];
	if (s[i] == t[j]) {
		res = dfs(i + 1, j + 1);
	}
	else {
		ll res1 = dfs(i + 1, j + 1) + 1LL; //変換
		ll res2 = dfs(i + 1, j) + 1LL;//削除
		ll res3 = dfs(i, j + 1) + 1LL;//挿入
		res = min(res1, min(res2, res3));
	}
	//printf("dfs(%d,%d)=%d\n", i, j, res);
	return memo[i][j] = res;
}

void solve() {
	memset(memo, -1, sizeof(memo));
	cout << dfs(0, 0) << endl;
}

int main() {
	cin >> n >> m;
	cin >> s;
	cin >> t;
	solve();
	return 0;
}