#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  cin >> n >> m;
  string a, b;
  cin >> a >> b;
  vector<vector<int>> dp(n + 1, vector<int>(m + 1));
  int ans = 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] = dp[i - 1][j - 1] + 2;
      else
        dp[i][j] = max(0, max(dp[i - 1][j] - 1, dp[i][j - 1] - 1));
      ans = max(ans, dp[i][j]);
    }
  }
  cout << ans;
}
