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

int solve(string s, string t, int n, int m, int itr = 0){
  if(itr == n)
    return 0;
  if(itr == m)
    return n - m;
  if(s[itr] == t[itr])
    return solve(s, t, n, m, itr + 1);

  int mincost;
  mincost = solve(s, t, n, m, itr + 1) + 1;
  mincost = min(mincost, solve(s, t.substr(1, m - 1), n, m - 1, itr) + 1);
  mincost = min(mincost, solve(s, "a" + t, n, m + 1, itr + 1) + 1);
  return mincost;
}

int main(){
  int n, m;
  cin >> n >> m;
  string s, t;
  cin >> s >> t;
  cout << solve(t, s, m, n) << endl;
}