#pragma GCC optimize("O3")
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <cfloat>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <fstream>
#include <functional>
#include <bitset>
using namespace std;

using ll = long long;
using P = pair<int, int>;
using T = tuple<int, int, int>;

template <class T> inline T chmax(T &a, const T b) {return a = (a < b) ? b : a;}
template <class T> inline T chmin(T &a, const T b) {return a = (a > b) ? b : a;}

constexpr int MOD = 1e9 + 7;
constexpr int inf = 1e9;
constexpr long long INF = 1e18;
constexpr double pi = acos(-1);
constexpr double EPS = 1e-10;

int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};

int edit_distance(string s, string t){
    int n = s.size(), m = t.size();
    vector<vector<int>> dp(n+1, vector<int>(m+1, 0));
    for(int i=0; i<=n; i++) dp[i][0] = i;
    for(int i=0; i<=m; i++) dp[0][i] = i;

    for(int i=0; i<n; i++){
        for(int j=0; j<m; j++){
            int cost = (s[i] == t[j] ? 0 : 1);
            dp[i+1][j+1] = min({dp[i][j+1] + 1, dp[i+1][j] + 1, dp[i][j] + cost});
        }
    }

    return dp[n][m];
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n, m; cin>>n>>m;
    string s, t; cin>>s>>t;

    cout << edit_distance(s, t) << endl;

    return 0;
}