#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <assert.h>
#include <numeric>
#include <time.h>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <ctime>
#include <functional>
#include <set>
#include <tuple>
#include <cassert>
#include <bitset>

using namespace std;
typedef long long ll;

#define rep(i, n) for (int i = 0; i < n; i++)
#define all(c) (c).begin(), (c).end()
#define P pair<int, int>
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define Graph vector<vector<int>>
#define fi first
#define se second
#define pb push_back
typedef vector<int> vint;
typedef vector<bool> vbool;
typedef pair<int, int> pint;
typedef vector<pint> vpint;

int main()
{
  int n, m;
  cin >> n >> m;
  string S, T;
  cin >> S >> T;

  int dp[n + 1][m + 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;
  }

  rep(i, n)
  {
    rep(j, m)
    {
      if (S[i] == T[j])
      {
        dp[i + 1][j + 1] = dp[i][j];
      }
      else
      {
        dp[i + 1][j + 1] = min(dp[i][j], min(dp[i + 1][j], dp[i][j + 1])) + 1;
      }
    }
  }

  cout << dp[n][m] << endl;
}