#include <bits/stdc++.h>

#define VARNAME(x) #x
#define show(x) cerr << #x << " = " << x << endl

using namespace std;
using ll = long long;
using ld = long double;
template <typename T>
vector<T> Vec(int n, T v)
{
    return vector<T>(n, v);
}
template <class... Args>
auto Vec(int n, Args... args)
{
    auto val = Vec(args...);
    return vector<decltype(val)>(n, move(val));
}

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz:" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = (ll)1e9 + 7LL;
constexpr ld PI = static_cast<ld>(3.1415926535898);

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 10;


int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, M;
    cin >> N >> M;
    string s, t;
    cin >> s >> t;

    auto dp = Vec(N + 1, M + 1, INF<ll>);
    dp[0][0] = 0;
    for (int i = 0; i <= N; i++) {
        for (int j = 0; j <= M; j++) {
            if (i < N and j < M) {
                dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j] + (s[i] == t[j] ? 0 : 1));
            }
            if (j < M) {
                dp[i][j + 1] = min(dp[i][j + 1], dp[i][j] + 1);
            }
            if (i < N) {
                dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + 1);
            }
        }
    }
    cout << dp[N][M] << endl;

    return 0;
}