#include <bits/stdc++.h>
using namespace std;
int max(int a, int b) { return (a > b ? a : b); }
int min(int a, int b) { return ((a < b) ? a : b); }
int gcd(int a, int b) {
  if (a == 0)
    return b;
  else
    return gcd(b % a, a);
}
int main() {
  int t = 1;
  while (t--) {
    int n, m;
    cin >> n >> m;
    string a, b;
    cin >> a >> b;
    vector<vector<int> > dp(n + 1, vector<int>(m + 1, 0));
    int res = 0;
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) {
        if (a[i - 1] == b[j - 1]) {
          dp[i][j] = max(0, max(dp[i][j], dp[i - 1][j - 1])) + 2;
        } else {
          dp[i][j] = max(0, max(dp[i - 1][j], dp[i][j - 1])) - 1;
        }
        res = max(res, dp[i][j]);
      }
    }
    cout << res << endl;
  }
}
