#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
const int INF = 1 << 30;
const int MOD = 1e9 + 7;

template<class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template<class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

int main() {
  int n, m;
  string S, T;
  cin >> n >> m >> S >> T;
  vector<vector<int>> dp(1001, vector<int>(1001, INF));
  dp[0][0] = 0;
  for (int i = 0; i < S.size(); i++) {
    for (int j = 0; j < T.size(); j++) {
      if (S[i] == T[j]) {
        dp[i + 1][j + 1] = min({
          dp[i][j],
          dp[i][j + 1] + 1,
          dp[i + 1][j] + 1
        });
      }
      else {
        dp[i + 1][j + 1] = min({
          dp[i][j] + 1,
          dp[i][j + 1] + 1,
          dp[i + 1][j] + 1
        }); 
      }
    }
  }
  cout << dp[S.size()][T.size()] << endl;
  return 0;
}