#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <stack>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

#define MAX 1000000000

int solve(const string& S, const string& T){
  std::vector< std::vector<int> > D(S.length()+1, std::vector<int>(T.length()+1, MAX));
  
  rep(i,S.length()+1) D[i][0] = i;
  rep(i,T.length()+1) D[0][i] = i;
  REP(i,1,S.length()+1){
    REP(j,1,T.length()+1){
      int op_nop = MAX;
      if(S[i-1] == T[j-1]){
        op_nop = D[i-1][j-1];
      }
      int op_ins = MAX;
      if(D[i][j-1] != MAX){
        op_ins = D[i][j-1] + 1;
      }
      int op_del = MAX;
      if(D[i-1][j] != MAX){
        op_del = D[i-1][j] + 1;
      }
      int op_rep = MAX;
      if(D[i-1][j-1] != MAX){
        op_rep = D[i-1][j-1] + 1;
      }

      D[i][j] = min(D[i][j], op_nop);
      D[i][j] = min(D[i][j], op_ins);
      D[i][j] = min(D[i][j], op_del);
      D[i][j] = min(D[i][j], op_rep);
    }
  }
  return D[S.length()][T.length()];
}


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

  cout << solve(S, T) << endl;

  return 0;
}