#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

int dp[1001][1001];

int lev(string s, string t) {
    rep(i, s.length() + 1) {
        rep (j, t.length() + 1) {
            if (min(i, j) == 0) {
                dp[i][j] = max(i, j);
            } else {
                dp[i][j] = min({dp[i - 1][j] + 1, dp[i][j - 1] + 1, dp[i - 1][j - 1] + (s[i - 1] != t[j - 1])});
            }
        }
    }

    return dp[s.length()][t.length()];
}


int main() {
    int n, m;
    string s, t;
    cin >> n >> m >> s >> t;

    cout << lev(s, t) << endl;
}