#include <bits/stdc++.h>
using namespace std;
template <typename A>
ostream &operator<<(ostream &cout, vector<A> const &v);
template <typename A, typename B>
ostream &operator<<(ostream &cout, pair<A, B> const &p) {
  return cout << "(" << p.first << ", " << p.second << ")";
}
template <typename A>
ostream &operator<<(ostream &cout, vector<A> const &v) {
  cout << "[";
  for (int i = 0; i < v.size(); i++) {
    if (i) cout << ", ";
    cout << v[i];
  }
  return cout << "]";
}
template <typename A, typename B>
istream &operator>>(istream &cin, pair<A, B> &p) {
  cin >> p.first;
  return cin >> p.second;
}
mt19937_64 rng(61378913);
void usaco(string filename) {
  freopen((filename + ".in").c_str(), "r", stdin);
  freopen((filename + ".out").c_str(), "w", stdout);
}
const long double pi = 3.14159265358979323846;
long long n, m, k, q, l, r, x, y, z;
const long long template_array_size = 1e6 + 6884;
long long a[template_array_size];
long long b[template_array_size];
long long c[template_array_size];
string second, t;
long long ans = 0;
int dp[5005][5005];
void solve(int tc = 0) {
  cin >> n >> m >> second >> t;
  memset(dp, 0, sizeof(dp));
  int ans = 0;
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < m; j++) {
      int score = 4 * (second[i] == t[j]) - 2;
      int prev = 0;
      if (i > 0 && j > 0) prev = max(prev, dp[i - 1][j - 1]);
      int cur = score + prev;
      if (i > 0) cur = max(cur, dp[i - 1][j] - 1);
      if (j > 0) cur = max(cur, dp[i][j - 1] - 1);
      dp[i][j] = cur;
      ans = max(ans, cur);
    }
  }
  cout << ans << '\n';
}
int main() {
  { ios_base::sync_with_stdio(false); }
  { cin.tie(NULL); }
  cout << setprecision(12) << fixed;
  int tc = 1;
  for (int t = 0; t < tc; t++) solve(t);
}
