#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

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

    vector<vector<unsigned>> dp(n+1, vector<unsigned>(m+1, -1));

    dp[0][0]=0;
    for(int i=1; i<=n; ++i) dp[i][0]=i;
    for(int j=1; j<=m; ++j) dp[0][j]=j;

    for(int i=0; i<n; ++i) {
        for(int j=0; j<m; ++j) {
            dp[i+1][j+1]=min({dp[i][j]+(s[i]!=t[j]), dp[i][j+1]+1, dp[i+1][j]+1});
        }
    }
    cout<<(int)dp[n][m]<<endl;
}