#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

int LevenshteinDist(const string& s, const string& t)
{
    int n = s.size();
    int m = t.size();
    vector<vector<int> > minCost(n+2, vector<int>(m+2, INT_MAX));
    minCost[0][0] = 0;
    for(int i=0; i<=n; ++i){
        for(int j=0; j<=m; ++j){
            minCost[i+1][j] = min(minCost[i+1][j], minCost[i][j] + 1);
            minCost[i][j+1] = min(minCost[i][j+1], minCost[i][j] + 1);
            if(i < n && j < m && s[i] == t[j])
                minCost[i+1][j+1] = min(minCost[i+1][j+1], minCost[i][j]);
            else
                minCost[i+1][j+1] = min(minCost[i+1][j+1], minCost[i][j] + 1);
        }
    }
    return minCost[n][m];
}

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

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

    return 0;
}