#include <bits/stdc++.h>
using namespace std;
using ld = long double;
template <class T>
inline T gcd(T a, T b) {
  return !a ? b : gcd(b % a, a);
}
template <class T>
inline T lcm(T a, T b) {
  return (a * b) / gcd(a, b);
}
mt19937 rnd(time(0));
const int INF = 1e9;
const long long LLINF = 1e15;
void solve() {
  int n, m;
  cin >> n >> m;
  string a, b;
  cin >> a >> b;
  int ans = 0;
  vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      dp[i][j] = max(0, max(dp[i - 1][j], dp[i][j - 1]) - 1);
      if (a[i - 1] == b[j - 1]) {
        dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 2);
      }
      ans = max(ans, dp[i][j]);
    }
  }
  cout << ans << '\n';
  return;
}
signed main() {
  ios_base ::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  int t = 1;
  while (t-- > 0) {
    solve();
  }
  return 0;
}
