#include <bits/stdc++.h>
#define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i < (n + 1); ++i)
const double PI = 3.141592653589793238463;
using namespace std;
using ll = long long;
const ll INF = 1LL << 50;
typedef pair<int, int> P;
const int mod = 1e9 + 7;
const int dx[] = {0,1,0,-1}, dy[] = {1,0,-1,0};
const int ddx[] = {0,1,0,-1,1,1,-1,-1}, ddy[] = {1,0,-1,0,1,-1,1,-1};

int main() {
    string  S,T;
    int n,m;
    cin >> n >> m;
    cin >> S >> T;
    int dp[1010][1010];
    memset(dp, 0, sizeof(dp));
    rep(i,S.size()) {
        rep(j, T.size()) {
            if(S[i]==T[j]) dp[i+1][j+1] = dp[i][j];
            else dp[i+1][j+1] = min(min(dp[i+1][j] + 1,dp[i][j+1] + 1), dp[i][j]+1);
        }
    }
    cout << dp[S.size()][T.size()] << endl;
    return 0;
}